Collector grid, electrode structures and interrconnect structures for photovoltaic arrays and methods of manufacture

ABSTRACT

The invention teaches novel structure and methods for producing electrical current collectors and electrical interconnection structure. Such articles find particular use in facile production of modular arrays of photovoltaic cells. The current collector and interconnecting structures may be initially produced separately from the photovoltaic cells thereby allowing the use of unique materials and manufacture. Subsequent combination of the structures with photovoltaic cells allows facile and efficient completion of modular arrays. Methods for combining the collector and interconnection structures with cells and final interconnecting into modular arrays are taught.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/290,896 filed Nov. 5, 2008 now abandoned, entitled Collector Grid,Electrode Structures and Interconnect Structures for Photovoltaic Arraysand Methods of Manufacture, which is a Continuation-in-Part of U.S.patent application Ser. No. 11/824,047 filed Jun. 30, 2007 nowabandoned, entitled Collector Grid, Electrode Structures andInterconnect Structures for Photovoltaic Arrays and other OptoelectricDevices, which is a Continuation-in-Part of U.S. application Ser. No.11/404,168 filed Apr. 13, 2006, entitled Substrate and Collector GridStructures for Integrated Photovoltaic Arrays and Process of Manufactureof Such Arrays, and now U.S. Pat. No. 7,635,810. The entire contents ofthe above identified applications are incorporated herein by thisreference.

BACKGROUND OF THE INVENTION

This invention teaches novel structure and methods for achievingefficient collection and conveyance of power from photovoltaic powergenerating devices.

Photovoltaic cells have developed according to two distinct methods. Theinitial operational cells employed a matrix of single crystal siliconappropriately doped to produce a planar p-n junction. An intrinsicelectric field established at the p-n junction produces a voltage bydirecting solar photon produced holes and free electrons in oppositedirections. Despite good conversion efficiencies and long-termreliability, widespread energy collection using single-crystal siliconcells is thwarted by the high cost of single crystal silicon materialand interconnection processing.

A second approach to produce photovoltaic cells is by depositing thinphotovoltaic semiconductor films on a supporting substrate. Materialrequirements are minimized and technologies can be proposed for massproduction. Thin film photovoltaic cells employing amorphous silicon,cadmium telluride, copper indium gallium diselenide, dye sensitizedsolar cells (DSSC), printed silicon inks and the like have receivedincreasing attention in recent years.

Despite significant improvements in individual cell conversionefficiencies for both single crystal and thin film approaches,photovoltaic energy collection has been generally restricted toapplications having low power requirements. One factor characteristic ofmany optoelectric devices and photovoltaic cells in particular is thatelectrical energy is produced over a relatively expansive surface area.Thus a challenge to implementing bulk power systems is the problem ofeconomically collecting the photogenerated power from an expansivesurface. In particular, photovoltaic cells can be described as highcurrent, low voltage devices. Typically individual cell voltage is lessthan about two volts, and often less than 0.6 volt. The currentcomponent is a substantial characteristic of the power generated.Efficient power collection from expansive photovoltaic cell surfacesmust minimize resistive losses associated with the high currentcharacteristic. In the specific case of most photovoltaic cells, theupper surface is normally formed by a transparent conductive oxide(TCO). However, these TCO layers are relatively resistive compared topure metals and have a surface resistivity on the order of 10 to 100ohms per square. Thus the conductive surface itself is limited in itsability to collect and transport current and efforts must be made tominimize resistive losses in transport of current through the TCO layer.This problem increases in severity as individual cell sizes increase.One solution is to simply reduce individual cell size (and thusaccumulated current from an individual cell) to a point where thetransparent conductive oxide alone can handle the current. Where largerindividual cell sizes are the norm, it is common practice to augment thetransparent conductive oxide with a current collector structurecomprising a pattern of highly conductive traces extending oversubstantially the entire surface from which current is to be collected.Often the structure is in the form of a grid or lattice pattern. Thecurrent collector structure reduces the distance that current must betransported by the transparent conductive oxide before it reaches ahighly conductive conveyance path off the surface. Thus the currentcollector structure collects current from a surface having relativelylow surface conductivity. Many current collector structures or grids areconventionally prepared by first applying metal wires, fused silverfilled pastes or silver filled ink traces to the cell surface and thencovering the surface with a sealing material in a subsequent operation.These highly conductive traces may lead to a collection buss such as acopper foil strip which also functions as a tab extending to the backelectrode of an adjacent cell. The wire approach requires positioningand fixing of multiple fine fragile wires which makes mass productiondifficult and expensive. Silver pastes are expensive and require highfusion temperatures which not all photovoltaic semiconductors cantolerate. A silver filled ink, as compared to a fuseable paste, issimply dried or cured at mild temperatures which do not adversely affectthe cell. However, this ink approach requires the use of relativelyexpensive inks because of the high loading of finely divided silverparticles. In addition, batch printing on the individual cells islaborious and expensive. Finally, the silver filled ink is relativelyresistive compared to a fuseable silver paste or metal wire. Typicalsilver filled inks have intrinsic resistivities in the range 0.00002 to0.01 ohm-cm.

Thus there remains a need for improved materials and structure forcollecting the current from the top light incident surface ofphotovoltaic cells.

Normally one envisions a photovoltaic power collection device muchlarger than the size of an individual cell. Therefore, an arrangementmust be supplied to collect power from multiple cells. This is normallyaccomplished by interconnecting multiple cells in series. In this way,voltage is stepped through each cell while current and associatedresistive losses are minimized. Such interconnected multi-cellarrangements are commonly referred to as “modules” or “arrays”. However,it is readily recognized that making effective, durable seriesconnections among multiple small cells can be laborious, difficult andexpensive. Regarding traditional crystalline silicon cells, theindividual cells are normally discrete and comprise rigid wafersapproximately 200 micrometers thick and approximately 230 squarecentimeters in area. A common way to convert multiple such cells intomodules is to use a conventional “string and tab” arrangement. In thisprocess multiple discrete cells are arranged in “strings” and thetopside current collector electrodes of cells are connected to backsideelectrodes of adjacent cells using “tabs” or ribbons of conductivematerial. The cell connections often involve tedious manual operationssuch as soldering and handling of multiple interconnected cells. Next,unwieldy flexible leads from the terminal cells must be directed andsecured in position for outside connections, again a tedious operation.Finally, weight and assembly concerns limit the ultimate size of themodule. These limitations impede adoption of the modules for large scalepower generation.

In order to approach economical mass production of modules of seriesconnected individual cells, a number of factors must be considered inaddition to the type of photovoltaic materials chosen. These include thesubstrate employed and the process envisioned. Since thin films can bedeposited over expansive areas, thin film technologies offer additionalopportunities for mass production of interconnected modules compared toinherently small, discrete single crystal silicon cells. Thus a numberof U.S. patents have issued proposing designs and processes to achieveseries interconnections among thin film photovoltaic cells. Many ofthese technologies comprise deposition of photovoltaic thin films onglass substrates followed by scribing to form smaller area individualcells. Multiple steps then follow to electrically connect the individualcells in series while maintaining the original common glass substrate.These “common” substrate approaches have come to be known as “monolithicintegration”. Examples of these proposed processes are presented in U.S.Pat. Nos. 4,443,651, 4,724,011, and 4,769,086 to Swartz, Turner et al.and Tanner et al. respectively. While expanding the opportunities formass production of interconnected cell modules compared with inherentlydiscrete approaches for crystal silicon cells, monolithic integrationemploying common glass substrates must inherently be performed on anindividual batch basis. In addition, many monolithic approaches are notcompatible with the use of a current collector grid and therefore cellsizes (in the direction of current flow) are constrained. Typically,cell widths for monolithic integration between 0.5 cm. and 1.0 cm. aretaught in the art. However, as cell widths decrease, the width of thearea between individual cells (interconnect area) should also decreaseso that the relative portion of inactive surface of the interconnectarea does not become excessive. These small cell widths demand very fineinterconnect area widths, which dictate delicate and sensitivetechniques to be used to electrically connect the top TCO surface of onecell to the bottom electrode of an adjacent series connected cell.Furthermore, achieving good stable ohmic contact to the TCO cell surfacehas proven difficult, especially when one employs those sensitivetechniques available when using the TCO only as the top collectorelectrode.

More recently, developers have explored depositing wide area films usingcontinuous roll-to-roll processing. This technology generally involvesdepositing thin films of photovoltaic material onto a continuouslymoving web. However, a challenge still remains regarding subdividing theexpansive films into individual cells followed by interconnecting into aseries connected array. For example, U.S. Pat. No. 4,965,655 to Grimmeret. al. and U.S. Pat. No. 4,697,041 to Okamiwa teach processes requiringexpensive laser scribing and interconnections achieved with laser heatstaking. In addition, these two references teach a substrate of thinvacuum deposited metal on films of relatively expensive polymers. Theelectrical resistance of thin vacuum metallized layers may significantlylimit the active area of the individual interconnected cells.

It has become well known in the art that the efficiencies of certainpromising thin film photovoltaic junctions can be substantiallyincreased by high temperature treatments. These treatments involvetemperatures at which even the most heat resistant plastics suffer rapiddeterioration. Use of a metal foil as a substrate allows hightemperature treatments and continuous roll-to-roll processing. However,the subsequent conversion to an interconnected module of multiple cellshas proven difficult, in part because the metal foil substrate iselectrically conducting.

U.S. Pat. No. 4,746,618 to Nath et al. teaches a design and process toachieve interconnected arrays using roll-to-roll processing of a metalweb substrate such as stainless steel. The process includes multipleoperations of cutting, selective deposition, and riveting. Theseoperations add considerably to the final interconnected array cost.

U.S. Pat. No. 5,385,848 to Grimmer teaches roll-to-roll methods toachieve integrated series connections of adjacent thin film photovoltaiccells supported on an electrically conductive metal substrate. Theprocess includes mechanical or chemical etch removal of a portion of thephotovoltaic semiconductor and transparent top electrode to expose aportion of the electrically conductive metal substrate. The exposedmetal serves as a contact area for interconnecting adjacent cells. Thesematerial removal techniques are troublesome for a number of reasons.First, many of the chemical elements involved in the best photovoltaicsemiconductors are expensive and environmentally unfriendly. Thisremoval subsequent to controlled deposition involves containment, dustand dirt collection and disposal, and possible cell contamination. Thisis not only wasteful but considerably adds to expense. Secondly, theremoval processes are difficult to control dimensionally. Thus asignificant amount of the valuable photovoltaic semiconductor is lost tothe removal process. Ultimate module efficiencies are furthercompromised in that the spacing between adjacent cells grows, therebyreducing the effective active collector area for a given module area.

Thus there remains a need for acceptable mass manufacturing processesand articles to achieve effective integrated interconnections amongphotovoltaic cells.

A further issue that has impeded adoption of photovoltaic technology,especially for bulk power collection in the form of solar farms,involves installation of multiple modules over expansive regions ofsurface. Traditionally, modules have been mounted individually onsupporting mounts, normally at an incline to horizontal appropriate tothe latitude of the site. Conducting leads from each module are thenphysically coupled with leads from an adjacent module in order tointerconnect multiple modules. This arrangement results in a string ofmodules each of which is coupled to an adjacent module. At one end ofthe string, the power is transferred from the end module to be conveyedto a separate site for further treatment such as voltage adjustment.This arrangement avoids having to run conductive cabling from eachindividual module to the separate treatment site.

The traditional solar farm installation described in the above paragraphhas some drawbacks. First, traditional modules are limited in size dueto weight and manufacturing constraints. This fact increases the numberof individual modules required to cover a desired surface area. Next,the module itself comprises a string of individual cells. In theconventional module lead conductors in the form of flexible wires orribbons are attached to an electrode on the two cells positioned at eachend of the string in order to convey the power from the module. Aftermounting the individual modules on their support at the installationsite, the respective leads from adjacent modules must be connected inorder to couple adjacent modules, and the connection must be protectedto avoid environmental deterioration or separation. These areintrinsically tedious manual operations. Finally, since the module leadsand cell interconnections are not of high current carrying capacity, theadjacent cells are normally connected in series arrangement. Thusvoltage builds up to high levels even at relatively short strings ofmodules. While not an overriding problem security and insulation must beappropriate to eliminate a shock hazard.

Thus there remains a need for improved module form factors andcomplimentary installation structure to reduce the cost and complexityof achieving large area “utility” scale photovoltaic installations.

In a somewhat removed segment of technology, a number of electricallyconductive fillers have been used to produce electrically conductivepolymeric materials. This technology generally involves mixing of aconductive filler such as silver particles with the polymer resin priorto fabrication of the material into its final shape. Conductive fillersmay have high aspect ratio structure such as metal fibers, metal flakesor powder, or highly structured carbon blacks, with the choice based ona number of cost/performance considerations. More recently, fineparticles of intrinsically conductive polymers have been employed asconductive fillers within a resin binder. Electrically conductivepolymers have been used as bulk thermoplastic compositions, orformulated into paints and inks. Their development has been spurred inlarge part by electromagnetic radiation shielding and static dischargerequirements for plastic components used in the electronics industry.Other known applications include resistive heating fibers and batterycomponents and production of conductive patterns and traces. Thecharacterization “electrically conductive polymer” covers a very widerange of intrinsic resistivities depending on the filler, the fillerloading and the methods of manufacture of the filler/polymer blend.Resistivities for filled electrically conductive polymers may be as lowas 0.00001 ohm-cm. for very heavily filled silver inks, yet may be ashigh as 10,000 ohm-cm or even more for lightly filled carbon blackmaterials or other “anti-static” materials. “Electrically conductivepolymer” has become a broad industry term to characterize all suchmaterials. In addition, it has been reported that recently developedintrinsically conducting polymers (absent conductive filler) may exhibitresistivities comparable to pure metals.

In yet another separate technological segment, coating plasticsubstrates with metal electrodeposits has been employed to achievedecorative effects on items such as knobs, cosmetic closures, faucets,and automotive trim. The normal conventional process actually combinestwo primary deposition technologies. The first is to deposit an adherentmetal coating using chemical (electroless) deposition to first coat thenonconductive plastic and thereby render its surface highly conductive.This electroless step is then followed by conventional electroplating.ABS (acrylonitrile-butadiene-styrene) plastic dominates as the substrateof choice for most applications because of a blend of mechanical andprocess properties and ability to be uniformly etched. The overallplating process comprises many steps. First, the plastic substrate ischemically etched to microscopically roughen the surface. This isfollowed by depositing an initial metal layer by chemical reduction(typically referred to as “electroless plating”). This initial metallayer is normally copper or nickel of thickness typically one-halfmicrometer. The object is then electroplated with metals such as brightnickel and chromium to achieve the desired thickness and decorativeeffects. The process is very sensitive to processing variables used tofabricate the plastic substrate, limiting applications to carefullyprepared parts and designs. In addition, the many steps employing harshchemicals make the process intrinsically costly and environmentallydifficult. Finally, the sensitivity of ABS plastic to liquidhydrocarbons has prevented certain applications. ABS and other suchpolymers have been referred to as “electroplateable” polymers or resins.This is a misnomer in the strict sense, since ABS (and othernonconductive polymers) are incapable of accepting an electrodepositdirectly and must be first metallized by other means before beingfinally coated with an electrodeposit. The conventional technology forelectroplating on plastic (etching, chemical reduction, electroplating)has been extensively documented and discussed in the public andcommercial literature. See, for example, Saubestre, Transactions of theInstitute of Metal Finishing, 1969, Vol. 47, or Arcilesi et al.,Products Finishing, March 1984.

Many attempts have been made to simplify the process of electroplatingon plastic substrates. Some involve special chemical techniques toproduce an electrically conductive film on the surface. Typical examplesof this approach are taught by U.S. Pat. No. 3,523,875 to Minklei, U.S.Pat. No. 3,682,786 to Brown et. al., and U.S. Pat. No. 3,619,382 toLupinski. The electrically conductive film produced was thenelectroplated. None of these attempts at simplification have achievedany recognizable commercial application.

A number of proposals have been made to make the plastic itselfconductive enough to allow it to be electroplated directly therebyavoiding the “electroless plating” process. As noted above, it is commonto produce electrically conductive polymers by incorporating conductiveor semiconductive fillers into a polymeric binder. Investigators haveattempted to produce electrically conductive polymers capable ofaccepting an electrodeposited metal coating by loading polymers withrelatively small conductive particulate fillers such as graphite, carbonblack, and silver or nickel powder or flake. Heavy such loadings aresufficient to reduce volume resistivity to a level where electroplatingmay be considered. However, attempts to make an acceptableelectroplateable polymer using the relatively small metal containingfillers alone encounter a number of barriers. First, the most conductivefine metal containing fillers such as silver are relatively expensive.The loadings required to achieve the particle-to-particle proximity toachieve acceptable conductivity increases the cost of the polymer/fillerblend dramatically. The metal containing fillers are accompanied byfurther problems. They tend to cause deterioration of the mechanicalproperties and processing characteristics of many resins. Thissignificantly limits options in resin selection. All polymer processingis best achieved by formulating resins with processing characteristicsspecifically tailored to the specific process (injection molding,extrusion, blow molding, printing etc.). A required heavy loading ofmetal filler severely restricts ability to manipulate processingproperties in this way. A further problem is that metal fillers can beabrasive to processing machinery and may require specialized screws,barrels, and the like.

Another major obstacle involved in the electroplating of electricallyconductive polymers is a consideration of adhesion between theelectrodeposited metal and polymeric substrate (metal/polymer adhesion).In most cases sufficient adhesion is required to prevent metal/polymerseparation during extended environmental and use cycles. Despite beingelectrically conductive, a simple metal-filled polymer offers no assuredbonding mechanism to produce adhesion of an electrodeposit since themetal particles may be encapsulated by the resin binder, often resultingin a resin-rich “skin”.

A number of methods to enhance electrodeposit adhesion to electricallyconductive polymers have been proposed. For example, etching of thesurface prior to plating can be considered. Etching can be achieved byimmersion in vigorous solutions such as chromic/sulfuric acid.Alternatively, or in addition, an etchable species can be incorporatedinto the conductive polymeric compound. The etchable species at exposedsurfaces is removed by immersion in an etchant prior to electroplating.Oxidizing surface treatments can also be considered to improvemetal/plastic adhesion. These include processes such as flame or plasmatreatments or immersion in oxidizing acids. In the case of conductivepolymers containing finely divided metal, one can propose achievingdirect metal-to-metal adhesion between electrodeposit and filler.However, here the metal particles are generally encapsulated by theresin binder, often resulting in a resin rich “skin”. To overcome thiseffect, one could propose methods to remove the “skin”, exposing activemetal filler to bond to subsequently electrodeposited metal.

Another approach to impart adhesion between conductive resin substratesand electrodeposits is incorporation of an “adhesion promoter” at thesurface of the electrically conductive resin substrate. This approachwas taught by Chien et al. in U.S. Pat. No. 4,278,510 where maleicanhydride modified propylene polymers were taught as an adhesionpromoter. Luch, in U.S. Pat. No. 3,865,699 taught that certain sulfurbearing chemicals could function to improve adhesion of initiallyelectrodeposited Group VIII metals.

For the above reasons, electrically conductive polymers employing metalfillers have not been widely used as bulk substrates forelectroplateable articles. Such metal containing polymers have found useas inks or pastes in production of printed circuitry. Revived effortsand advances have been made in the past few years to accomplishelectroplating onto printed conductive patterns formed by silver filledinks and pastes.

An additional physical obstacle confronting practical electroplatingonto electrically conductive polymers is the initial “bridge” ofelectrodeposit onto the surface of the electrically conductive polymer.In electrodeposition, the substrate to be plated is often made cathodicthrough a pressure contact to a metal rack tip, itself under cathodicpotential. However, if the contact resistance is excessive or thesubstrate is insufficiently conductive, the electrodeposit currentfavors the rack tip to the point where the electrodeposit will notbridge to the substrate.

Moreover, a further problem is encountered even if specialized rackingor cathodic contact successfully achieves electrodeposit bridging to thesubstrate. Many of the electrically conductive polymers haveresistivities far higher than those of typical metal substrates. Also,many applications involve electroplating onto a thin (less than 25micrometer) printed substrate. The conductive polymeric substrate may berelatively limited in the amount of electrodeposition current which italone can convey. Thus, the conductive polymeric substrate does notcover almost instantly with electrodeposit as is typical with metallicsubstrates. Except for the most heavily loaded and highly conductivepolymer substrates, a large portion of the electrodeposition currentmust pass back through the previously electrodeposited metal growinglaterally over the surface of the conductive plastic substrate. In afashion similar to the bridging problem discussed above, theelectrodeposition current favors the electrodeposited metal and thelateral growth can be extremely slow and erratic. This restricts thesize and “growth length” of the substrate conductive pattern, increasesplating costs, and can also result in large non-uniformities inelectrodeposit integrity and thickness over the pattern.

This lateral growth is dependent on the ability of the substrate toconvey current. Thus, the thickness and resistivity of the conductivepolymeric substrate can be defining factors in the ability to achievesatisfactory electrodeposit coverage rates. When dealing withselectively electroplated patterns long thin metal traces are oftendesired. Electrodeposited metal thicknesses of from 1 to 25 micrometerare often typical. The metal traces must normally be of relativelyuniform thickness and have a minimum of internal stress. Further, anelectrically conductive polymer “seed” pattern defining the traces isoften relatively thin, less than about 25 micrometers, and therefore mayhave relatively low current carrying capacity. These factors of courseoften work against achieving the desired result.

This coverage rate problem likely can be characterized by a continuum,being dependent on many factors such as the nature of the initiallyelectrodeposited metal, electroplating bath chemistry, the nature of thepolymeric binder and the resistivity of the electrically conductivepolymeric substrate. As a “rule of thumb”, the instant inventorestimates that coverage rate issue would demand attention if theresistivity of a bulk conductive polymeric substrate rose above about0.001 ohm-cm. Alternatively, a “rule of thumb” appropriate for thin filmsubstrates would be that attention is appropriate if the substrate filmto be plated had a surface “sheet” resistance of greater than about0.075 ohm per square.

The least expensive (and least conductive) of the readily availableconductive fillers for plastics are carbon blacks. Attempts have beenmade to electroplate electrically conductive polymers using carbon blackloadings. Examples of this approach are the teachings of U.S. Pat. Nos.4,038,042, 3,865,699, and 4,278,510 to Adelman, Luch, and Chien et al.respectively. These earlier efforts were directed primarily at achievingdecorative electroplated articles with the substrate fully encapsulatedwith electrodeposit.

Adelman taught incorporation of conductive carbon black into a polymericmatrix to achieve electrical conductivity required for electroplating.The substrate was pre-etched in chromic/sulfuric acid to achieveadhesion of the subsequently electroplated metal. A fundamental problemremaining unresolved by the Adelman teaching is the relatively highresistivity of carbon loaded polymers. The lowest “microscopicresistivity” generally achievable with carbon black loaded polymers isabout 1 ohm-cm. This is about five to six orders of magnitude higherthan typical electrodeposited metals such as copper or nickel. Thus, theelectrodeposit bridging and coverage rate problems described aboveremained unresolved by the Adelman teachings.

Luch in U.S. Pat. No. 3,865,699 and Chien et al. in U.S. Pat. No.4,278,510 also chose carbon black as a filler to provide an electricallyconductive surface for the polymeric compounds to be electroplated. TheLuch U.S. Pat. No. 3,865,699 and the Chien U.S. Pat. No. 4,278,510 arehereby incorporated in their entirety by this reference. However, theseinventors further taught inclusion of materials to increase the rate ofmetal coverage or the rate of metal deposition on the polymer. Thesematerials can be described herein as “electrodeposit growth rateaccelerators” or “electrodeposit coverage rate accelerators”. Anelectrodeposit coverage rate accelerator is a material functioning toincrease the electrodeposition coverage rate over the surface of anelectrically conductive polymer independent of any incidental affect itmay have on the conductivity of an electrically conductive polymer. Inthe embodiments, examples and teachings of U.S. Pat. Nos. 3,865,699 and4,278,510, it was shown that certain sulfur bearing materials, includingelemental sulfur, can function as electrodeposit coverage or growth rateaccelerators to overcome problems in achieving electrodeposit coverageof electrically conductive polymeric surfaces having relatively highresistivity or thin electrically conductive polymeric substrates havinglimited current carrying capacity.

In addition to elemental sulfur, sulfur in the form of sulfur donorssuch as sulfur chloride, 2-mercapto-benzothiazole,N-cyclohexyle-2-benzothiaozole sulfonomide, dibutyl xanthogen disulfide,and tetramethyl thiuram disulfide or combinations of these and sulfurwere identified. Those skilled in the art will recognize that thesesulfur donors are the materials which have been used or have beenproposed for use as vulcanizing agents or accelerators. Since thepolymer-based compositions taught by Luch and Chien et al. could beelectroplated directly they could be accurately defined as directlyelectroplateable resins (DER). These directly electroplateable resins(DER) can be generally described as electrically conductive polymerswith the inclusion of a growth rate accelerator.

Specifically for the present invention, specification, and claims,directly electroplateable resins, (DER), are characterized by thefollowing features:

-   -   (a) presence of an electrically conductive polymer;    -   (b) presence of an electrodeposit coverage rate accelerator;    -   (c) presence of the electrically conductive polymer and the        electrodeposit coverage rate accelerator in the directly        electroplateable composition in cooperative amounts required to        achieve direct coverage of the composition with an        electrodeposited metal or metal-based alloy.

In his patents, Luch specifically identified unsaturated elastomers suchas natural rubber, polychloroprene, butyl rubber, chlorinated butylrubber, polybutadiene rubber, acrylonitrile-butadiene rubber,styrene-butadiene rubber etc. as suitable for the matrix polymer of adirectly electroplateable resin. Other polymers identified by Luch asuseful included polyvinyls, polyolefins, polystyrenes, polyamides,polyesters and polyurethanes.

Using the materials and loadings reported, the carbon black/polymerformulations of Adelman, Luch and Chien referenced above would beexpected to have intrinsic “microscopic” resistivities of less thanabout 1000 ohm-cm. (i.e. 1 ohm-cm., 10 ohm-cm., 100 ohm-cm., 1000ohm-cm.). When used alone, the minimum workable level of carbon blackrequired to achieve “microscopic” electrical resistivities of less than1000 ohm-cm. for a polymer/carbon black mix appears to be about 8 weightpercent based on the combined weight of polymer plus carbon black. The“microscopic” material resistivity generally is not reduced below about1 ohm-cm. by using conductive carbon black alone. This is several ordersof magnitude larger than typical metal resistivities or resistivitiesassociated with common silver filled inks.

It is understood that in addition to carbon blacks, other well known,highly conductive fillers can be considered to decrease the“microscopic” resistivity of DER compositions. Examples include but arenot limited to metallic fillers or flake such as silver. In these casesthe more highly conductive fillers can be used to augment or evenreplace the conductive carbon black. Furthermore, one may consider usingintrinsically conductive polymers to supply the required conductivity.For example, an intrinsically conductive polymer in particulate form maybe considered as a conductive filler.

The “bulk, macroscopic” resistivity of conductive carbon black filledpolymers can be further reduced by augmenting the carbon black fillerwith additional highly conductive, high aspect ratio fillers such asmetal containing fibers. This can be an important consideration in thesuccess of certain applications. Furthermore, one should realize thatincorporation of non-conductive fillers may increase the “bulk,macroscopic” resistivity of conductive polymers loaded with finelydivided conductive fillers without significantly altering the“microscopic resistivity” of the conductive polymer “matrix”encapsulating the non-conductive filler particles. It has been foundthat DER formulations can include substantial quantities ofnon-conductive fillers. In particular, loading of DER formulations withglass fibers has been shown to dramatically reduce mold shrinkage andincrease stiffness of these formulations.

Regarding electrodeposit coverage rate accelerators, both Luch and Chienet al. in the above discussed U.S. patents demonstrated that sulfur andother sulfur bearing materials such as sulfur donors and vulcanizationaccelerators function as electrodeposit coverage rate accelerators whenusing an initial Group VIII metal electrodeposit “strike” layer. Thus,an electrodeposit coverage rate accelerator need not be electricallyconductive, but may be a material that is normally characterized as anon-conductor. The coverage rate accelerator need not appreciably affectthe conductivity of the polymeric substrate. As an aid in understandingthe function of an electrodeposit coverage rate accelerator thefollowing is offered:

-   -   a. A specific conductive polymeric structure is identified as        having insufficient current carrying capacity to be directly        electroplated in a practical manner.    -   b. A material is added to the conductive polymeric material        forming said structure. Said material addition may have        insignificant affect on the current carrying capacity of the        structure (i.e. it does not appreciably reduce resistivity or        increase thickness). The material need only be present at the        substrate surface.    -   c. Nevertheless, inclusion of said material greatly increases        the speed at which an electrodeposited metal laterally covers        the electrically conductive surface.        It is contemplated that a coverage rate accelerator may be        present as an additive, as a species absorbed on a filler        surface, or even as a functional group attached to the polymer        chain. One or more growth rate accelerators may be present in a        directly electroplateable resin (DER) to achieve combined, often        synergistic results.

A hypothetical example might be an extended trace of conductive inkhaving a dry thickness of 1 micrometer. Such inks typically include aconductive filler such as silver, nickel, copper, conductive carbon etc.The limited thickness of the ink reduces the current carrying capacityof this trace thus preventing direct electroplating in a practicalmanner. However, inclusion of an appropriate quantity of a coverage rateaccelerator may allow the conductive trace to be directly electroplatedin a practical manner.

One might expect that other Group 6A elements, such as oxygen, seleniumand tellurium, could function in a way similar to sulfur. In addition,other combinations of electrodeposited metals, such as copper andappropriate coverage rate accelerators may be identified. It isimportant to recognize that such an electrodeposit coverage rateaccelerator is important in order to achieve direct electrodeposition ina practical way onto polymeric substrates having low conductivity orvery thin electrically conductive polymeric substrates having restrictedcurrent carrying ability.

It has also been found that the inclusion of an electrodeposit coveragerate accelerator promotes electrodeposit bridging from a discretecathodic metal contact to a DER surface. This greatly reduces thebridging problems described above.

Due to multiple performance problems associated with their intended enduse, the instant inventor is unaware of any recognizable commercialsuccess for attempts to directly electroplate electrically conductivepolymers in applications intended to produce decorative “bright”electroplated objects. Nevertheless, electroplating in a selectivemanner onto insulating substrates for functional applications remains anintriguing possibility for many applications. This is becauseelectroplating is selective between conductive and insulating surfacesand is inexpensive. Further, a wide variety of metals and alloys can bedeposited by electroplating and the deposition rates are relativelyrapid. There are a number of techniques available to achieve selectiveelectrodeposited patterns on insulating substrates. Most involve initialformation of a “seed” pattern. The “seed” pattern is formed from amaterial that has the ability to assist in subsequent metalelectrodeposition. Typical “seed” patterns comprise metals, polymerscontaining electroless plating catalysts, and electrically conductivepolymers. Examples of such processes follow in subparagraphs 1 through3.

(1) An electrically conductive polymer is formed into a “seed” patternby printing from an ink formulation onto the surface of an insulatingsubstrate. This electrically conductive polymer “seed layer” pattern,when dried, is then subjected to a metal electroplating process to coverthe pattern with a conductive metal.

(2) A polymeric composition containing a catalyst suitable forinitiating chemical metal deposition is printed into a “seed layer”pattern. After appropriate activation, the article is subjected to achemical metal deposition “electroless” plating bath. Following coveragewith electroless metal, the “seed pattern”, now comprising a layeredstructure of polymer and chemically deposited metal, is subjected to anelectroplating process to cover the pattern with electrodeposited metal.

(3) An insulating substrate is coated in its entirety with a thin filmof metal. This uniform coating may be achieved, for example, usingvacuum metallizing, sputtering, chemical metal deposition processing. Asa next step, a mask is applied having a pattern the reverse of theeventual desired selective metal pattern. The remaining exposed pattern(reverse of the mask pattern) retains its conductive surface and therebyforms a “seed” pattern for subsequent further metal electrodeposition.This subsequent electrodeposition increases metal thickness and also mayapply a final coat resistant to an eventual etch. The mask is thenremoved and the article etched to completely remove the metal that hadbeen covered by the mask.

As previously noted, the current inventor is unaware of any recognizablesuccess in attempts to use DER technology to produce decorative “bright”electroplated objects. Nevertheless, the current inventor has persistedin personal efforts to overcome certain performance deficienciesassociated with the initial DER technology. Along with these efforts hascome a recognition of unique and eminently suitable applicationsemploying the DER technology for functional applications. Thesefunctional applications often have requirements, such as selectivity,fine patterning and relatively thin electrodeposits, which differsubstantially from the requirements of purely decorative electroplating.Some examples of these unique applications for electroplated articlesinclude solar cell electrical current collection grids and interconnectstructures, electrodes, electrical circuits, electrical traces, circuitboards, antennas, capacitors, induction heaters, connectors, switches,and resistors. One readily recognizes that the demand for suchfunctional applications for electroplated articles is relatively recentand has been particularly explosive during the past decade.

It is important to recognize a number of important characteristics ofdirectly electroplateable resins (DER's) which may facilitate certainembodiments of the current invention. One such characteristic of the DERtechnology is its ability to employ polymer resins and formulationsgenerally chosen in recognition of the fabrication process envisionedand the intended end use requirements. In order to provide clarity,examples of some such fabrication processes are presented immediatelybelow in subparagraphs 1 through 9.

-   -   (1) Should it be desired to electroplate an ink, paint, coating,        or paste which may be printed or formed on a substrate, a good        film forming polymer, for example a soluble resin such as an        elastomer, can be chosen to fabricate a DER ink (paint, coating,        paste etc.). For example, in some embodiments thermoplastic        elastomers having an olefin base, a urethane base, a block        copolymer base or a random copolymer base may be appropriate. In        some embodiments the coating may comprise a water based latex.        Other embodiments may employ more rigid film forming polymers.        The DER ink composition can be tailored for a specific process        such flexographic printing, rotary silk screening, gravure        printing, ink jet printing, flow coating, spraying etc.        Furthermore, additives such as tackifiers or curatives can be        employed to improve the adhesion of the DER ink to various        substrates.    -   (2) Very thin DER traces often associated with collector grid        structures can be printed and then electroplated due to the        inclusion of the electrodeposit growth rate accelerator. Traces        as thin as 1.5 micrometer have been demonstrated as practical.        Silk screening has produced trace widths as little as 150        micrometers.    -   (3) Should it be desired to cure the DER substrate to a 3        dimensional matrix, an unsaturated elastomer or other “curable”        resin may be chosen.    -   (4) DER inks can be formulated to form electrical traces on a        variety of flexible substrates. For example, should it be        desired to form electrical structure on a laminating film, a DER        ink adherent to the sealing surface of the laminating film can        be effectively electroplated with metal and subsequently        laminated to a separate surface.    -   (5) Should it be desired to electroplate a fabric, a DER ink can        be used to coat all or selected portion of the fabric intended        to be electroplated. Furthermore, since DER's can be fabricated        out of the thermoplastic materials commonly used to create        fabrics, the fabric itself could completely or partially        comprise a DER. This would eliminate the need to coat the        fabric.    -   (6) Should one desire to electroplate a thermoformed article or        structure, DER's would represent an eminently suitable material        choice. DER's can be easily formulated using olefinic materials        which are often a preferred material for the thermoforming        process. Furthermore, DER's can be easily and inexpensively        extruded into the sheet like structure necessary for the        thermoforming process.    -   (7) Should one desire to electroplate an extruded article or        structure, for example a sheet or film, DER's can be formulated        to possess the necessary melt strength advantageous for the        extrusion process.    -   (8) Should one desire to injection mold an article or structure        having thin walls, broad surface areas etc. a DER composition        comprising a high flow polymer can be chosen.    -   (9) Should one desire to vary adhesion between an        electrodeposited DER structure supported by a substrate the DER        material can be formulated to supply the required adhesive        characteristics to the substrate. For example, the polymer        chosen to fabricate a DER ink can be chosen to cooperate with an        “ink adhesion promoting” surface treatment such as a material        primer or corona treatment. In this regard, it has been observed        that it may be advantageous to limit such adhesion promoting        treatments to a single side of the substrate. Treatment of both        sides of the substrate in a roll to roll process may adversely        affect the surface of the DER material and may lead to        deterioration in plateability. For example, it has been observed        that primers on both sides of a roll of PET film have adversely        affected plateability of DER inks printed on the PET. It is        believed that this is due to primer being transferred to the        surface of the DER ink when the PET is rolled up.

All polymer fabrication processes require specific resin processingcharacteristics for success. The ability to “custom formulate” DER's tocomply with these changing processing and end use requirements whilestill allowing facile, quality electroplating is unique among methods toelectroplate onto polymeric forms.

Another important recognition regarding the suitability of DER's for theteachings of the current invention is the simplicity of theelectroplating process. Unlike many conventional electroplated plastics,DER's do not require a significant number of process steps prior toactual electroplating. This allows for simplified manufacturing andimproved process control. It also reduces the risk of crosscontamination such as solution dragout from one process bath beingtransported to another process bath. The simplified manufacturingprocess will also result in reduced manufacturing costs.

Yet another recognition of the benefit of DER's for the teachings of thecurrent invention is the ability they offer to selectively electroplatemetal onto an article or structure. The desired metal structures of theinvention often involve long yet fine metal traces. Further, thearticles of the invention often consist of such metal patternsselectively positioned in conjunction with flexible insulatingmaterials. Such selective positioning of metals can often be expensiveand difficult. As discussed previously, the coverage rate acceleratorsincluded in DER formulations allow for such extended surfaces to becovered with electrodeposit in a relatively rapid and simple manner.

Yet another recognition of the benefit of DER's is their ability they tobe continuously electroplated. As will be shown in later embodiments, itis often desired to continuously electroplate metal onto “seed” patternsdefining specific structure. DER's are eminently suitable as “seed”patterns for such continuous electroplating.

Yet another recognition of the benefit of DER's for the teachings of thecurrent invention is their ability to withstand the pre-treatments oftenrequired to prepare other materials for plating. For example, were a DERto be combined with a metal, the DER material would be resistant to manyof the pre-treatments such as cleaning which may be necessary toelectroplate the metal.

Another important recognition is the suitability of metalelectrodeposition for producing articles of the current invention.Electroplating is a rapid and inexpensive metal deposition process.Electroplating allows selective deposition of a wide variety of metalsand alloys. Single or multi-layered deposits may be chosen for specificattributes. Examples may include copper for conductivity and nickel,silver or gold for corrosion resistance. Electrodeposition furtherallows a wide range of appropriate deposit thickness to be achievedrelatively quickly. The articles of the invention may require metaltraces varying from about 0.1 micrometer to greater than about 100micrometer (i.e. 0.1 micrometer, 1 micrometer, 10 micrometer 25micrometer, 100 micrometer etc.). Such thicknesses may be readilyachieved in reasonable time using metal electrodeposition.

These and other attributes of DER's and electroplating may contribute tosuccessful articles and processing of the instant invention. However, itis emphasized that the DER technology, and more broadly electroplatingonto conductive polymeric “seed” layers, is but one of a number ofalternative metal deposition or positioning processes suitable toproduce many of the embodiments of the instant invention. Otherapproaches, such as electroless metal deposition, selective metaletching, placement of metal forms such as wires or strips, stampingmetal patterns and selective vacuum or chemical deposition may besuitable alternatives for producing the selectively positioned metalstructures of the invention. These choices will become clear to theskilled artisan in light of the teachings to follow in the remainingspecification, accompanying figures and claims.

Another important aspect of the embodiments of the current invention isthe inclusion of web processing to achieve structure and combinations ina facile and economic fashion. A web is a generally planar or sheet-likestructure, normally flexible, having thickness much smaller than itslength or width. This sheet-like structure may also have a length fargreater than its width. A web of extended length may be conveyed throughone or more processing steps in a way that can be described as“continuous”, thereby achieving the advantages of continuous processing.“Continuous” web processing is well known in the paper and packagingindustries. It is normally accomplished by supplying web material from afeed roll of extended length to the process steps. The product resultingfrom the process is often continuously retrieved onto a takeup rollfollowing processing, in which case the process may be termedroll-to-roll or reel-to-reel processing.

An advantage of web processing is that the web can comprise manydifferent materials, surface characteristics and forms. The web maycomprise layers for packaging material options such as pressuresensitive or hot melt adhesive layers, environmental barriers, and assupport for printing and other features. The web can constitute anonporous film or may be a fabric and may be transparent or opaque.Combinations of such differences over the expansive surface of the webcan be achieved. Indeed, as will be shown, the web itself can comprisematerials such as conductive polymers or even metal fibers which willallow the web itself to perform electrical function. The web materialmay remain as part of the final article of manufacture or may be removedafter processing, in which case it would serve as a surrogate ortemporary support during processing.

In order to eliminate ambiguity in terminology, for the presentinvention the following definitions are supplied:

While not precisely definable, for the purposes of this specification,electrically insulating materials may generally be characterized ashaving electrical resistivities greater than 10,000 ohm-cm. Also,electrically conductive materials may generally be characterized ashaving electrical resistivities less than 0.001 ohm-cm. Alsoelectrically resistive or semi-conductive materials may generally becharacterized as having electrical resistivities in the range of about0.01 ohm-cm to about 10,000 ohm-cm. The characterization “electricallyconductive polymer” covers a very wide range of intrinsic resistivitiesdepending on the filler, the filler loading and the methods ofmanufacture of the filler/polymer blend. Resistivities for electricallyconductive polymers may be as low as 0.00001 ohm-cm. for very heavilyfilled silver inks, yet may be as high as 10,000 ohm-cm or even more forlightly filled carbon black materials or other “anti-static” materials.“Electrically conductive polymer” has become a broad industry term tocharacterize all such materials. Thus, the term “electrically conductivepolymer” as used in the art and in this specification and claims extendsto materials of a very wide range of resitivities from about 0.00001ohm-cm. to about 10,000 ohm-cm and higher.

An “electroplateable material” is a material having suitable attributesthat allow it to be coated with a layer of electrodeposited material.

A “metallizable material” is a material suitable to be coated with ametal deposited by any one or more of the available metallizing process,including chemical deposition, vacuum metallizing, sputtering, metalspraying, sintering and electrodeposition.

“Metal-based” refers to a material or structure having at least onemetallic property and comprising one or more components at least one ofwhich is a metal or metal-containing alloy.

“Alloy” refers to a substance composed of two or more intimately mixedmaterials.

“Group VIII metal-based” refers to a substance containing by weight 50%to 100% metal from Group VIII of the Periodic Table of Elements.

A “bulk metal foil” refers to a thin structure of metal or metal-basedmaterial that may maintain its integrity absent a supporting structure.Generally, metal films of thickness greater than about 2 micrometers mayhave this characteristic. Thus, in most cases a “bulk metal foil” willhave a thickness between about 2 micrometers and 250 micrometers (i.e. 2micrometer, 5 micrometer, 10 micrometer, 25 micrometer, 100 micrometer,250 micrometer) and may comprise a laminate of multiple layers.

The term “monolithic” or “monolithic structure” is used in thisspecification and claims as is common in industry to describe an objectthat is made or formed into or from a single item or material.

The term “continuous form” refers to a material structure having onedimension of sufficient size such that it can be fed to or retrievedfrom a process over an extended time period without interruption of thematerial structure.

The term “continuous process” refers to a process or method in which atleast one of the material feed components or a product of the processhas a continuous form.

A web is a generally planar or sheet-like structure, normally flexible,having thickness much smaller than its length or width.

“Web processing” is a process wherein a web itself is altered by theprocess or wherein structure supported by the web is added, altered orotherwise modified by the process.

A “reel to reel” or “roll to roll” process is one wherein at least oneof the feed components to a process is supplied in a continuous rollform and the product of the process is retrieved on a takeup roll.

OBJECTS OF THE INVENTION

An object of the invention is to eliminate the deficiencies in the priorart methods of producing expansive area, series or parallelinterconnected photovoltaic modules and arrays.

A further object of the present invention is to provide improvedsubstrates to achieve series or parallel interconnections amongphotovoltaic cells.

A further object of the invention is to provide structures useful forcollecting current from an electrically conductive surface.

A further object of the invention is to provide structures useful incollecting current from a surface of limited current carrying capacitysuch as those of many optoelectric devices including photovoltaic cells.The current collector structure comprising a pattern of highlyconductive traces normally extends over a preponderance of the surfacefrom which current is to be collected.

A further object of the present invention is to provide improvedprocesses whereby interconnected photovoltaic modules can beeconomically mass produced.

A further object of the invention is to provide a process and means toaccomplish interconnection of photovoltaic cells into an integratedarray through continuous processing.

Other objects and advantages will become apparent in light of thefollowing description taken in conjunction with the drawings andembodiments.

SUMMARY OF THE INVENTION

The current invention provides a solution to the stated needs byproducing the active photovoltaic cells and interconnecting structuresseparately and subsequently combining them to produce the desiredinterconnected array or module. One embodiment of the inventioncontemplates deposition of thin film photovoltaic junctions on metalfoil substrates which may be heat treated following deposition ifrequired in a continuous fashion without deterioration of the metalsupport structure. In a separate operation, interconnection structuresare produced. In an embodiment, interconnection structures are producedin a continuous roll-to-roll fashion. In an embodiment, theinterconnecting structure is laminated to the foil supportedphotovoltaic cell and conductive connections are applied to complete thearray. Application of a separate interconnection structure subsequent tocell manufacture allows the interconnection structures to be uniquelyformulated using polymer-based materials. Interconnections are achievedwithout the need to use the expensive and intricate material removaloperations currently taught in the art to achieve interconnections.

In another embodiment, a separately prepared current collector gridstructure is taught. In an embodiment the current collector structure isproduced in a continuous roll-to-roll fashion. The current collectorstructure comprises conductive material pattern positioned on a firstsurface of a laminating sheet or positioning carrier sheet. Thiscombination is prepared such that a first surface of the laminating orpositioning sheet and the conductive material can be positioned inabutting contact with a conductive surface. In one embodiment theconductive surface is the light incident surface of a photovoltaic cell.In another embodiment the conductive surface is the rear conductivesurface of a photovoltaic cell.

BRIEF DESCRIPTION OF THE DRAWINGS

The various factors and details of the structures and manufacturingmethods of the present invention are hereinafter more fully set forthwith reference to the accompanying drawings wherein:

FIG. 1 is a top plan view of a thin film photovoltaic structureincluding its support structure.

FIG. 1A is a top plan view of the article of FIG. 1 following anoptional processing step of subdividing the article of FIG. 1 into cellsof smaller dimension.

FIG. 2 is a sectional view taken substantially along the line 2-2 ofFIG. 1.

FIG. 2A is a sectional view taken substantially along the line 2A-2A ofFIG. 1A.

FIG. 2B is a simplified sectional depiction of the structure embodied inFIG. 2A.

FIG. 3 is an expanded sectional view showing a form of the structure ofsemiconductor 11 of FIGS. 2 and 2A.

FIG. 4 illustrates a possible process for producing the structure shownin FIGS. 1-3.

FIG. 5 is a sectional view illustrating the problems associated withmaking series connections among thin film photovoltaic cells shown inFIGS. 1-3.

FIG. 6 is a top plan view of a starting structure for an embodiment ofthe instant invention.

FIG. 7 is a sectional view, taken substantially along the lines 7-7 ofFIG. 6, illustrating a possible laminate structure of the embodiment.

FIG. 8 is a simplified sectional depiction of the FIG. 7 structuresuitable for ease of presentation of additional embodiments.

FIG. 9 is a top plan view of the structure embodied in FIGS. 6 through 8following an additional processing step.

FIG. 10 is a sectional view taken substantially from the perspective oflines 10-10 of FIG. 9.

FIG. 11 is a sectional view taken substantially from the perspective oflines 11-11 of FIG. 9.

FIG. 12 is a top plan view of an article resulting from exposing theFIG. 9 article to an additional processing step.

FIG. 13 is a sectional view taken substantially from the perspective oflines 13-13 of FIG. 12.

FIG. 14 is a sectional view taken substantially from the perspective oflines 14-14 of FIG. 12.

FIG. 15 is a sectional view taken substantially from the perspective oflines 15-15 of FIG. 12.

FIG. 16 is a top plan of an alternate embodiment similar in structure tothe embodiment of FIG. 9.

FIG. 17 is a sectional view taken substantially from the perspective oflines 17-17 of FIG. 16.

FIG. 18 is a sectional view taken substantially from the perspective oflines 18-18 of FIG. 16.

FIG. 19 is a simplified sectional view of the article embodied in FIGS.16-18 suitable for ease of clarity of presentation of additionalembodiments.

FIG. 20 is a sectional view showing the article of FIGS. 16 through 19following an additional optional processing step.

FIG. 21 is a simplified depiction of a process useful in producingobjects of the instant invention.

FIG. 22 is a sectional view taken substantially from the perspective oflines 22-22 of FIG. 21 showing an arrangement of three components justprior to the Process 92 depicted in FIG. 21.

FIG. 23 is a sectional view showing the result of combining thecomponents of FIG. 22 using the process of FIG. 21.

FIG. 24 is a sectional view embodying a series interconnection ofmultiple articles as depicted in FIG. 23

FIG. 25 is an exploded sectional view of the region within the box “K”of FIG. 24.

FIG. 26 is a top plan view of a starting article in the production ofanother embodiment of the instant invention.

FIG. 27 is a sectional view taken from the perspective of lines 27-27 ofFIG. 26.

FIG. 28 is a simplified sectional depiction of the article of FIGS. 26and 27 useful in preserving clarity of presentation of additionalembodiments.

FIG. 29 is a top plan view of the original article of FIGS. 26-28following an additional processing step.

FIG. 30 is a sectional view taken substantially from the perspective oflines 30-30 of FIG. 29.

FIG. 31 is a sectional view of the article of FIGS. 29 and 30 followingan additional optional processing step.

FIG. 32 is a sectional view, similar to FIG. 22, showing an arrangementof articles just prior to combination using a process such as depictedin FIG. 21.

FIG. 33 is a sectional view showing the result of combining thearrangement depicted in FIG. 32 using a process as depicted in FIG. 21.

FIG. 34 is a sectional view a series interconnection of a multiple ofarticles such as depicted in FIG. 33.

FIG. 35 is a top plan view of a starting article used to produce anotherembodiment of the instant invention.

FIG. 36 is a simplified sectional view taken substantially from theperspective of lines 36-36 of FIG. 35.

FIG. 37 is a expanded sectional view of the article embodied in FIGS. 35and 36 showing a possible multi-layered structure of the article.

FIG. 38 is a sectional view showing a structure combining repetitiveunits of the article embodied in FIGS. 35 and 36.

FIG. 39 is a top plan view of the article of FIGS. 35 and 36 followingan additional processing step.

FIG. 40 is a sectional view taken from the perspective of lines 40-40 ofFIG. 39.

FIG. 41 is a sectional view similar to that of FIG. 40 following anadditional optional processing step.

FIG. 42 is a sectional view showing a possible combining of the articleof FIG. 41 with a photovoltaic cell.

FIG. 43 is a sectional view showing multiple articles as in FIG. 42arranged in a series interconnected array.

FIG. 44 is a top plan view of a starting article in the production ofyet another embodiment of the instant invention.

FIG. 45 is a sectional view taken substantially from the perspective oflines 45-45 of FIG. 44 showing a possible layered structure for thearticle.

FIG. 46 is a sectional view similar to FIG. 45 but showing an alternatestructural embodiment.

FIG. 47 is a simplified sectional view of the articles embodied in FIGS.44-46 useful in maintaining clarity and simplicity for subsequentembodiments.

FIG. 48 is a top plan view of the articles of FIGS. 44-47 following anadditional processing step.

FIG. 49 is a sectional view taken substantially from the perspective oflines 49-49 of FIG. 48.

FIG. 50 is a top plan view of the article of FIGS. 48 and 49 followingan additional processing step.

FIG. 51 is a sectional view taken substantially from the perspective oflines 51-51 of FIG. 50.

FIG. 52 is a sectional view of the article of FIGS. 50 and 51 followingan additional optional processing step.

FIG. 53 is a top plan view of an article similar to that of FIG. 50 butembodying an alternate structure.

FIG. 54 is a sectional view taken substantially from the perspective oflines 54-54 of FIG. 53.

FIG. 55 is a sectional view showing an article combining the article ofFIG. 52 with a photovoltaic cell.

FIG. 56 is a sectional view embodying series interconnection of multiplearticles as depicted in FIG. 55.

FIG. 57 is a sectional view embodying a possible condition when using acircular form in a lamination process.

FIG. 58 is a sectional view embodying a possible condition resultingfrom choosing a low profile form in a lamination process.

FIG. 59 is a top plan view embodying a possible process to achievepositioning and combining of photovoltaic cells into a seriesinterconnected array.

FIG. 60 is a perspective view of the process embodied in FIG. 59.

FIG. 61 is a top plan view showing a simplified depiction of structureuseful to explain a concept of the invention.

FIG. 62 is a sectional view taken substantially from the perspective oflines 62-62 of FIG. 61.

DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. In the drawings, like reference numerals designate identical,equivalent or corresponding parts throughout several views and anadditional letter designation is characteristic of a particularembodiment.

Referring to FIGS. 1 and 2, an embodiment of a thin film photovoltaicstructure is generally indicated by numeral 1. It is noted here that“thin film” has become commonplace in the industry to designate certaintypes of semiconductor materials in photovoltaic applications. Theseinclude amorphous silicon, cadmium telluride, copper-indium-galliumdiselenide, dye sensitized polymers, so-called “Graetzel” electrolytecells and the like. While the characterization “thin film” may be usedto describe many of the embodiments of the instant invention, principlesof the invention may extend to photovoltaic devices not normallyconsidered “thin film” such as single crystal or polysilicon devices, asthose skilled in the art will readily appreciate. The article 1embodiment has a light-incident top surface 59 and a bottom surface 66.Structure 1 has a width X-1 and length Y-1. It is contemplated thatlength Y-1 may be considerably greater than width X-1 such that lengthY-1 can generally be described as “continuous” or being able to beprocessed in a roll-to-roll fashion. FIG. 2 shows that embodiment 1structure comprises a thin film semiconductor structure 11 supported by“bulk” metal-based foil 12. “Bulk” foil 12 is often self supporting toallow continuous processing. Foil 12 has a top surface 65, bottomsurface 66, and thickness “Z”. In the embodiment, bottom surface 66 offoil 12 also forms the bottom surface of photovoltaic structure 1.Metal-based foil 12 may be of uniform composition or may comprise alaminate of multiple layers. For example, foil 12 may comprise a baselayer of inexpensive and processable metal 13 with an additionalmetal-based layer 14 disposed between base layer 13 and semiconductorstructure 11. The additional metal-based layer 14 may be chosen toensure good ohmic contact between the top surface 65 of foil 12 andphotovoltaic semiconductor structure 11. Bottom surface 66 of foil 12may comprise a material 75 chosen to achieve good electrical andmechanical joining characteristics as will be shown. The thickness “Z”of foil 12 is often between 2 micrometers and 250 micrometers (i.e. 5micrometers, 10 micrometers, 25 micrometers, 50 micrometers, 100micrometers, 250 micrometers), and most often in the range of 10micrometer to 125 micrometer although thicknesses outside this range maybe functional in certain applications. One notes for example that shouldadditional support be possible, such as that supplied by a supportingplastic film, metal foil thickness may be far less (0.1 to 1 micrometer)than those characteristic of a “bulk” foil. Nevertheless, a foilthickness between 2 micrometers and 250 micrometers may be selfsupporting and provide adequate handling strength and integrity whilestill allowing flexibility for certain processing as further taughthereinafter.

In its simplest form, a photovoltaic structure combines an n-typesemiconductor with a p-type semiconductor to from a p-n junction. Oftenan optically transparent “window electrode”, such as a thin film of zincoxide, tin oxide indium tin oxide or the like is employed to minimizeresistive losses involved in current collection. FIG. 3 illustrates anexample of a typical photovoltaic structure in section. In FIGS. 2 and 3and other figures, an arrow labeled “hv” is used to indicate the lightincident side of the structure. In FIG. 3, 15 represents a thin film ofa p-type semiconductor, 16 a thin film of n-type semiconductor and 17the resulting photovoltaic junction. Window electrode 18 completes atypical photovoltaic structure. Various photovoltaic structures areknown. For example, cells can be multiple junction or single junctionand comprise homo or hetero junctions. Semiconductor structure 11 maycomprise any of the thin film structures known in the art, including butnot limited to CIS, CIGS, CdTe, Cu2S, amorphous silicon, so-called“Graetzel” electrolyte cells, organic solar cells such as dye sensitizedcells, polymer based semiconductors, cells based on silicon inks and thelike. Further, semiconductor structure 11 may also representcharacteristically “non-thin film” cells such as those based on singlecrystal or polycrystal silicon since many embodiments of the inventionmay encompass such cells, as will be evident to those skilled in the artin light of the teachings to follow.

“Window electrode” 18 normally comprises a conductive metal oxide. Thesematerials are applied as a thin layer, normally having a thickness lessthan about 1 micrometer. In addition, these materials have much higherintrinsic resistivity (in the range 0.001 ohm-cm.) than metals such ascopper. Thus the light incident surface of the cell, despite beingcharacterized as conductive, has limited current carrying capacity.

In the following, photovoltaic cells having a “bulk” metal based supportfoil will be used to illustrate many of the embodiments and teachings ofthe invention. The metal based foil may often serve as the backelectrode of the cell. However, those skilled in the art will recognizethat many of the applications of the instant invention may not use a“bulk” foil as represented in FIGS. 1 and 2. In many embodiments, othersubstrate structures, such as a metallized polymer film or glass, or athin conductive polymer layer, may be employed as a back electroderather than a “bulk” metal foil.

FIG. 4 refers to a method of manufacture of bulk thin film photovoltaicstructures generally illustrated in FIGS. 1 and 2. In the FIG. 4embodiment, a metal-based support foil 12 is moved in the direction ofits length Y through a deposition process, generally indicated as 19.Often foil 12 possesses structural characteristics such that it may becharacterized as self supporting. Process 19 accomplishes deposition ofthe active photovoltaic structure onto foil 12. Foil 12 is unwound fromsupply roll 20 a, passed through deposition process 19 and rewound ontotakeup roll 20 b. Process 19 can comprise any of the processeswell-known in the art for depositing thin film photovoltaic structures.These processes include electroplating, vacuum evaporation andsputtering, chemical deposition, and printing of nanoparticleprecursors. Process 19 may also include treatments, such as heattreatments, intended to enhance photovoltaic cell performance.

Those skilled in the art will readily realize that the depositionprocess 19 of FIG. 4 may often most efficiently produce photovoltaicstructure 1 having dimensions far greater than those suitable forindividual cells in an interconnected array. Thus, the photovoltaicstructure 1 may be subdivided into cells 10 having dimensions X-10 andY-10 as indicated in FIGS. 1A and 2A for further fabrication. In FIG.1A, width X-10 defines a first photovoltaic cell terminal edge 45 andsecond photovoltaic cell terminal edge 46. In one embodiment, forexample, X-10 of FIG. 1A may be from 0.02 inches to 12 inches and Y-10of FIG. 1A may be characterized as “continuous”. In other embodimentsthe final form of cell 10 may be rectangular, such as 6 inch by 6 inch,4 inch by 3 inch or 8 inch by 2 inch. In other embodiments, thephotovoltaic structure 1 of FIG. 1 may be subdivided in the “X”dimension only thereby retaining the option of further processing in a“continuous” fashion in the “Y” direction. In the following, cellstructure 10 in a form having dimensions suitable for interconnectioninto a multi-cell array may be referred to as “cell stock” or simply ascells. “Cell stock” can be characterized as being either continuous ordiscreet.

FIG. 2B is a simplified depiction of cell 10 shown in FIG. 2A. In orderto facilitate presentation of the aspects of the instant invention, thesimplified depiction of cell 10 shown in FIG. 2B will normally be used.

Referring now to FIG. 5, there are illustrated cells 10 as shown in FIG.2A. The cells have been positioned to achieve spatial positioning on thesupport substrate 21. Support structure 21 is by necessitynon-conductive at least in a space indicated by numeral 27 separatingthe adjacent cells 10. This insulating space prevents short circuitingfrom metal foil electrode 12 of one cell to foil electrode 12 of anadjacent cell. In order to achieve series connection, electricalcommunication must be made from the top surface of window electrode 18to the foil electrode 12 of an adjacent cell. This communication isshown in the FIG. 5 as a metal wire or tab 41. The direction of the netcurrent flow for the arrangement shown in FIG. 5 is indicated by thedouble pointed arrow “i”. It should be noted that foil electrode 12 isnormally relatively thin, on the order of 5 micrometer to 250micrometer. Moreover, in order to have the flexibility and physicalintegrity required for processing such as the roll-to-roll process 19 asembodied in FIG. 4, a foil thickness of between 10 micrometers and 250micrometer may be appropriate. Therefore, connecting to the foil edge asindicated in FIG. 5 would be impractical. Thus, such connections arenormally made to the top surface 65 or the bottom surface 66 of foil 12.One readily recognizes that connecting metal wire or tab 41 islaborious, making inexpensive production difficult.

FIG. 6 is a top plan view of a starting article in production of alaminating current collector grid or electrode according to the instantinvention. FIG. 6 embodies a polymer based film or glass substrate 70.Substrate 70 has width X-70 and length Y-70. When substrate 70 comprisesglass, it would typically be processed as discrete articles havingdefined width and length dimensions. In other embodiments involving, forexample, flexible films or webs and taught in detail below, Y-70 may bemuch greater than width X-70, whereby substrate film 70 can generally bedescribed as “continuous” in length and able to be processed in lengthdirection Y-70 in a continuous fashion. FIG. 7 is a sectional view takensubstantially from the view 7-7 of FIG. 6. Thickness dimension Z-70 issmall in comparison to dimensions Y-70, X-70. In a preferred embodimentsubstrate 70 may have a flexible sheetlike, or web structure. However,substrate flexibility is not a requirement for all embodiments of theinvention. As shown in FIG. 7, substrate 70 may be a laminate ofmultiple layers 72, 74, 76 etc. or may comprise a single layer ofmaterial. Any number of layers 72, 74, 76 etc. may be employed. Thelayers 72, 74, 76 etc. may comprise inorganic or organic components suchas thermoplastics, thermosets or silicon containing glass-like layers.The various layers are intended to supply functional attributes such asenvironmental barrier protection or adhesive characteristics. Suchfunctional layering is well-known and widely practiced in the plasticpackaging art. Sheetlike substrate 70 has first surface 80 and secondsurface 82. In particular, in light of the teachings to follow, one willrecognize that it may be advantageous to have layer 72 forming surface80 comprise a polymeric adhesive sealing material such as an ethylenevinyl acetate (EVA), ethylene ethyl acetate (EEA), an ionomer, or apolyolefin based adhesive to impart adhesive characteristics during apossible subsequent lamination process. It may be advantageous for theadhesive layer to have elastomeric characteristics to insure flexibilityand stress relief for the composite. Other sealing materials useful incertain embodiments include those comprising silicones, silicone gels,epoxies, polydimethyl siloxane (PDMS), RTV rubbers, polyvinyl butyral(PVB), thermoplastic polyurethanes (TPU), acrylics and urethanes. Anadhesive layer 72 forming surface 80 may further comprise a curingcomponent which would activate to produce a cross linked structure. Suchcross linking may improve adhesion of surface 80 to a mating surface oralso function to resist permanent deformation during thermal cycling.Suitable curatives may be activated by heat and/or radiation such asultraviolet (UV) radiation.

Lamination of such sheetlike films employing such sealing materials is acommon practice in the packaging industry. In the packaging industrylamination is known and understood as applying a film, normally polymerbased and normally having a surface comprising a sealing material, to asecond surface and sealing them together with heat and/or pressure.However, while a combination of heat and pressure is often used in thelamination process, the instant invention is applicable to laminatingmaterials, such as pressure sensitive adhesives, which may be appliedusing pressure alone. Suitable sealing materials may be made tacky andflowable, often under heated conditions, and retain their adhesive bondto many surfaces upon cooling and/or release of pressure. A wide varietyof laminating films with associated sealing materials is possible,depending on the surface to which the adhesive seal or bond is to bemade. Sealing materials such as olefin copolymers or atactic polyolefinsmay be advantageous, since these materials allow for the minimizing ofmaterials which may be detrimental to the longevity of a solar cell withwhich it is in contact. Additional layers 74, 76 etc. may comprisematerials which assist in support or processing such as polypropylene,polyethylene terepthalate and polycarbonate. Additional layers 74, 76may comprise barrier materials such as fluorinated polymers, biaxiallyoriented polypropylene (BOPP), Saran, and thin compound layers such asSiox. Saran is a tradename for poly (vinylidene chloride) manufacturedby Dow Chemical Corporation. Siox refers to a thin film of silicon oxideoften vapor deposited on a polymer support. Additional layers 74, 76etc. may also comprise materials intended to afford protection againstultraviolet radiation and may also comprise materials to promote curing.The instant invention does not depend on the presence of any specificmaterial for layers 72, 74, or 76. In many embodiments substrate 70 maybe generally be characterized as a laminating material. For example, theinvention has been successfully demonstrated using standard laminatingfilms sold by GBC Corp., Northbrook, Ill., 60062.

FIG. 8 depicts the structure of substrate 70 (possibly laminate) as asingle layer for purposes of presentation simplicity. Substrate 70 willbe represented as this single layer in the subsequent embodiments, butit will be understood that structure 70 may be a laminate of any numberof layers. In addition, substrate 70 is shown in FIGS. 6 through 8 as auniform, unvarying monolithic sheet. In this specification and claims,the term “monolithic” or “monolithic structure” is used as is common inindustry to describe an object that is made or formed into or from asingle item. However, it is understood that various regions of substrate70 may differ in composition through thickness Z-70. For example,selected regions of substrate 70 may comprise differing sheetlikestructures patched together using appropriate seaming techniques. Apurpose for such a “patchwork” structure will become clear in light ofthe teachings to follow.

FIG. 9 is a plan view of the structure following an additionalmanufacturing step.

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9.

FIG. 11 is a sectional view taken along line 11-11 of FIG. 9.

In the embodiment of FIGS. 9, 10, and 11, a structure is now designated71 to reflect the additional processing. It is seen in these embodimentsthat a repetitive pattern of multiple repetitively spaced “fingers” or“traces”, designated 84, extends from “buss” or “tab” structures,designated 86. In the embodiments of FIGS. 9, 10, and 11, both “fingers”84 and “busses” 86 are positioned on supporting substrate 70 in a gridpattern. In this embodiment, “fingers” 84 extend in the width X-71direction of article 71 and “busses” (“tabs”) extend in the Y-71direction substantially perpendicular to the “fingers”. Dimensions andstructure for the “fingers” and “busses” may vary with application. Forexample, if the article 71 is intended for collecting current from a toplight incident surface of a photovoltaic cell, one will understand thatshading by “fingers” 84 is of concern. Thus, the surface area of thefingers may normally be minimized consistent with adequate currentcarrying characteristics. Dimensions may also be dictated somewhat bythe materials and fabrication process used to create the fingers andbusses, and the dimensions of the individual cell. For example, shouldthe fingers be formed by a process such as silk screening of an ink, aminimum practical width of about 100 micrometer is typical. Should thefingers be formed by other techniques such as selective metal etching ormetal wire placement, widths less than 100 micrometers may be suitable.Spacing between the fingers may also vary depending on factors such ascurrent carrying capacity and surface conductivity of a matingconductive surface.

While a pattern of “fingers” and “busses” is shown in the FIG. 9embodiment, one will readily understand that other patterns appropriateto the eventual application of the article are possible and that thepattern of “fingers”/“busses” is but one of many structural patternspossible within the scope of the instant invention. Specifically, theinvention allows design flexibility associated with the process used toestablish the material pattern of “fingers” and “busses”. “Designflexible” processing includes printing of conductive inks or “seed”layers, foil etching or stamping, masked deposition using paint orvacuum deposition, and the like. As an example, the conductive paths canhave triangular type surface structures increasing in width (and thuscross section) in the direction of current flow. Thus the resistancedecreases as net current accumulates to reduce power losses. Variousstructural features, such as radiused connections between fingers andbusses may be employed to improve structural robustness. Further, theinvention permits a variety of structural forms to create the pattern.For example, while the embodiments of FIGS. 9 through 11 show the“fingers” and “busses” as essentially planar rectangular structures, thefingers or traces may be wires of circular cross section.

As indicated, structure 71 may be produced and processed extendingcontinuously in the length “Y-71” direction. Repetitive multiple“finger/buss” arrangements are shown in the FIG. 9 embodiment with arepeat dimension “F” as indicted. As will be seen, dimension “F” isassociated with the repeat distance among adjacent interconnectedphotovoltaic cells. When structure 71 is intended for eventual use as acurrent collector structure for the light incident surface of aphotovoltaic cell, portions of substrate 70 not overlayed by “fingers”84 and “busses” 86 remain transparent or translucent to visible light.In the embodiment of FIGS. 9 through 11, the “fingers” 84 and “busses”86 are shown to be a single layer for simplicity of presentation.However, the “fingers” and “busses” can comprise multiple layers ofdiffering materials chosen to support various functional attributes. Forexample the material in direct contact with substrate 70 defining the“buss” or “finger” patterns may be chosen for its adhesive affinity tosurface 80 of substrate 70 and also to a subsequently appliedconstituent of the buss or finger structure. Further, it may beadvantageous to have the first visible material component of the fingersand busses be of dark color or black. As will be shown, the lightincident side (outside surface) of the substrate 70 will eventually besurface 82. By having the first visible component of the fingers andbusses be dark, they will aesthetically blend with the generally darkcolor of the photovoltaic cell. This eliminates the often objectionableappearance of a metal colored grid pattern.

“Fingers” 84 and “busses” 86 may comprise electrically conductivematerial. Examples of such materials are metal wires and foils, stampedor die cut metal patterns, conductive metal containing inks and pastessuch as those having a conductive filler comprising silver or stainlesssteel, patterned deposited metals such as etched metal patterns ormasked vacuum deposited metals, intrinsically conductive polymers andDER formulations. In a preferred embodiment, the pattern of “fingers”and “busses” comprise electroplateable material such as DER or anelectrically conductive ink which will enhance or allow subsequent metalelectrodeposition. “Fingers” 84 and “busses” 86 may also comprisenon-conductive material which would assist accomplishing a subsequentdeposition of conductive material in the pattern defined by the“fingers” and “busses”. For example, “fingers” 84 or “busses” 86 couldcomprise a polymer which may be seeded to catalyze chemical depositionof a metal in a subsequent step. An example of such a material is seededABS. Patterns comprising electroplateable materials or materialsfacilitating subsequent electrodeposition are often referred to as“seed” patterns or layers. “Fingers” 84 and “busses” 86 may alsocomprise materials selected to promote adhesion of a subsequentlyapplied conductive material. “Fingers” 84 and “busses” 86 may differ inactual composition and be applied separately. For example, “fingers” 84may comprise a conductive ink while “buss/tab” 86 may comprise aconductive metal foil strip. Alternatively, fingers and busses maycomprise a continuous unvarying monolithic material structure formingportions of both fingers and busses. Fingers and busses need not both bepresent in certain embodiments of the invention.

One will recognize that while shown in the embodiments as a continuousvoid free surface, “buss” 86 could be selectively structured. Suchselective structuring may be appropriate to enhance functionality, suchas flexibility, of article 71 or any article produced there from.Furthermore, regions of substrate 70 supporting the “buss” regions 86may be different than those regions supporting “fingers” 84. Forexample, substrate 70 associated with “buss region” 86 may comprise afabric while substrate 70 may comprise a solid transparent film in theregion associated with “fingers” 84. A “holey” structure in the “bussregion” would provide increased flexibility, increased surface area andincreased structural characteristic for an adhesive to grip.

The embodiment of FIG. 9 shows multiple “busses” 86 extending in thedirection Y-71 with “fingers” extending from one side of the “busses” inthe X-71 direction. Many different such structural arrangements of thelaminating current collector structures are possible within the scopeand purview of the instant invention. It is important to note howeverthat the laminating current collector structures of the instantinvention may be manufactured utilizing continuous, bulk processing,including roll to roll processing. While the collector grid embodimentsof the current invention may advantageously be produced using continuousprocessing, one will recognize that combining of grids or electrodes soproduced with mating conductive surfaces may be accomplished usingeither continuous or batch processing. In one case it may be desired toproduce photovoltaic cells having discrete defined dimensions. Forexample, single crystal silicon cells are often produced having X-Ydimensions of about 6 inches by 6 inches. In this case the collectorgrids of the instant invention, which may be produced continuously, maythen be subdivided to dimensions appropriate for combining with suchcells. In other cases, such as production of many thin film photovoltaicstructures, a continuous roll-to-roll production of an expansive surfacearticle can be accomplished in the “Y” direction as identified inFIG. 1. Such a continuous expansive photovoltaic structure may becombined with a continuous arrangement of collector grids of the instantinvention in a semicontinuous or continuous manner. Alternatively theexpansive semiconductor structure may be subdivided into continuousstrips of cell stock. In this case, combining a continuous strip of cellstock with a continuous strip of collector grid of the instant inventionmay be accomplished in a continuous or semi-continuous manner.

FIGS. 12, 13 and 14 correspond to the views of FIGS. 9, 10 and 11respectively following an additional optional processing step. FIG. 15is a sectional view taken substantially along line 15-15 of FIG. 12.FIGS. 12 through 15 show additional conductive material deposited ontothe “fingers” 84 and “busses” 86 of FIGS. 9 through 11. In thisembodiment additional conductive material is designated by one or morelayers 88, 90 and the fingers and busses project above surface 80 asshown by dimension “H”. In some cases it may be desirable to reduce theheight of projection “H” prior to eventual combination with a conductivesurface such as 59 or 66 of photovoltaic cell 10. This reduction may beaccomplished by passing the structures as depicted in FIGS. 12-15through a pressurized and/or heated roller or the like to embed“fingers” 84 and/or “busses” 86 into layer 72 of substrate 70.

While shown as two layers 88, 90, it is understood that this conductivematerial could comprise more than two layers or be a single layer. Inaddition, while each additional conductive layer is shown in theembodiment as having the same continuous monolithic material extendingover both the buss and finger patterns, one will realize that selectivedeposition techniques would allow the additional “finger” layers todiffer from additional “buss” layers. For example, as best shown in FIG.14, “fingers” 84 have top free surface 98 and “busses” 86 have top freesurface 100. As noted, selective deposition techniques such as brushelectroplating or masked deposition would allow different materials tobe considered for the “buss” surface 100 and “finger” surface 98. In apreferred embodiment, at least one of the additional layers 88, 90 etc.are deposited by electrodeposition, taking advantage of the depositionspeed, compositional choice, low cost and selectivity of theelectrodeposition process. Many various metals, including highlyconductive silver, copper and gold, nickel, tin, indium and alloys ofthese can be readily electrodeposited. In these embodiments, it may beadvantageous to utilize electrodeposition technology giving anelectrodeposit of low tensile stress to prevent curling and promoteflatness of the metal deposits. In particular, use of nickel depositedfrom a nickel sulfamate bath, nickel deposited from a bath containingstress reducing additives such as brighteners, or copper from a standardacid copper bath have been found particularly suitable.Electrodeposition also permits precise control of thickness andcomposition to permit optimization of other requirements of the overallmanufacturing process for interconnected arrays. Thus, theelectrodeposited metal may significantly increase the current carryingcapacity of the “buss” and “finger” structure and may be the dominantcurrent carrying material for these structures. In general,electrodeposit thicknesses characterized as “low profile”, less thanabout 50 micrometer (i.e. 1 micrometer, 10 micrometer, 25 micrometer, 50micrometer), supply adequate current carrying capacity for the grid“fingers” of the instant invention. Thus electrodeposited metal offers avery appropriate material to achieve the dominant current carryingcapacity for the “buss” and “finger” structure. Alternatively, theseadditional conductive layers may be deposited by selective chemicaldeposition or registered masked vapor deposition. These additionallayers 88, 90 may also comprise conductive inks or adhesives applied byregistered printing.

It has been found very advantageous to form surface 98 of “fingers” 84or top surface 100 of “busses” 86 with a material compatible with theconductive surface with which eventual contact is made. In preferredembodiments, electroless deposition or electrodeposition is used to forma suitable metallic surface. Specifically electrodeposition offers awide choice of potentially suitable materials to form the top surface.Corrosion resistant materials such as nickel, chromium, tin, indium,silver, gold and platinum are readily electrodeposited. These functionaltop coatings, sometimes referred to as “flash” coatings, are often thin,less than about two micrometer (i.e. 0.1 micrometer, 1 micrometer, 2micrometer). The “flash” coatings normally need not exhibit exceptionalcurrent carrying capacity since the bulk of the current may be carriedby the underlying material such as the above described electroplatedmetals such as copper. When compatible, of course, surfaces comprisingmetals such as copper or zinc or alloys of copper or zinc may beconsidered. Alternatively, surfaces 98 and 100 may comprise a conversioncoating, such as a chromate coating, of a material such as copper orzinc. Further, as will be discussed below, it may be highly advantageousto choose a material to form surfaces 98 or 100 which exhibits adhesiveor bonding ability to a subsequently positioned abutting conductivesurface. For example, it may be advantageous to form surfaces 98 and 100using an electrically conductive adhesive. Such an adhesive could beapplied intermittently, for example as a series of “dots” over theunderlying conductive surface. Alternatively, it may be advantageous toform surfaces 98 of “fingers” 84 or 100 of “busses” 86 with a conductivematerial such as a low melting point metal such as tin, tin containingalloys, indium, lead etc. in order to facilitate electrical joining to acomplimentary conductive surface. Such low melting point materials canbe caused to melt at temperatures below that of many polymer processingoperations such as lamination. These processes are normally carried outat temperatures below about 325 degree C. (i.e. 100 degree C., 150degree C., 250 degree C.). One will note that materials forming“fingers” surface 98 and “buss” surface 100 need not be the same. It isemphasized that many of the principles taught in detail with referenceto FIGS. 6 through 15 extend to additional embodiments of the inventiontaught in subsequent Figures.

FIG. 16 is a top plan view of an article 102 embodying another form ofthe electrodes of the current invention. FIG. 16 shows article 102having structure comprising “fingers” 84 a extending from “buss/tab” 86a arranged on a substrate 70 a. The structure of FIG. 16 is similar tothat shown in FIG. 9. However, whereas FIG. 9 depicted multiple fingerand buss/tab structures arranged in a substantially repetitive patternin direction “X-71”, the FIG. 16 embodiment consists of one finger/busspattern. Thus, the dimension “X-102” of FIG. 16 may be roughlyequivalent to the repeat dimension “F” shown in FIG. 9. Indeed, it iscontemplated that article 102 of FIG. 16 may be produced by subdividingthe FIG. 9 structure 71 according to repeat dimension “F” shown in FIG.9. Dimension “Y-102” may be chosen appropriate to the particularprocessing scheme envisioned for the eventual lamination to a conductivesurface such as a photovoltaic cell. However, it is envisioned that“Y-102” may be much greater than “X-102” such that article 102 may becharacterized as continuous or capable of being processed in acontinuous, possibly roll-to-roll fashion. Article 102 has a firstterminal edge 104 and second terminal edge 106. In the FIG. 16embodiment “fingers” 84 a are seen to terminate prior to intersectionwith terminal edge 106. One will understand that this is not arequirement.

“Fingers” 84 a and “buss/tab” 86 a of FIG. 16 have the samecharacterization as “fingers” 84 and “busses” 86 of FIGS. 9 through 11.Like the “fingers” 84 and “busses” 86 of FIGS. 9 through 11, “fingers”84 a and “buss” 86 a of FIG. 16 may comprise materials that are eitherconductive, assist in a subsequent deposition of conductive material orpromote adhesion of a subsequently applied conductive material tosubstrate 70 a. While shown as a single layer, one appreciates that“fingers” 84 a and “buss” 86 a may comprise multiple layers. Thematerials forming “fingers” 84 a and “buss” 86 a may be different or thesame. In addition, the substrate 70 a may comprise different materialsor structures in those regions associated with “fingers” 84 a and “bussregion” 86 a. For example, substrate 70 a associated with “buss region”86 a may comprise a fabric to provide thru-hole communication andenhance flexibility, while substrate 70 a in the region associated with“fingers” 84 a may comprise a film devoid of thru-holes such as depictedin FIGS. 6-8. A “holey” structure in the “buss region” would provideincreased flexibility, surface area and structural characteristic for anadhesive to grip.

FIGS. 17 and 18 are sectional embodiments taken substantially from theperspective of lines 17-17 and 18-18 respectively of FIG. 16. FIGS. 17and 18 show that article 102 has thickness Z-102 which may be muchsmaller than the X and Y dimensions, thereby allowing article 102 to beflexible and processable in roll form. Also, flexible sheet-like article102 may comprise any number of discrete layers (three layers 72 a, 74 a,76 a are shown in FIGS. 17 and 18). These layers contribute tofunctionality as previously pointed out in the discussion of FIG. 7. Aswill be understood in light of the following discussion, it is normallyhelpful for layer 72 a forming free surface 80 a to exhibit adhesivecharacteristics to the eventual abutting conductive surface.

FIG. 19 is an alternate representation of the sectional view of FIG. 18.FIG. 19 depicts substrate 70 a as a single layer for ease ofpresentation. The single layer representation will be used in manyfollowing embodiments, but one will understand that substrate 70 a maycomprise multiple layers.

FIG. 20 is a sectional view of the article now identified as 110,similar to FIG. 19, after an additional optional processing step. In afashion like that described above for production of the currentcollector structure of FIGS. 12 through 15, additional conductivematerial (88 a/90 a) has been deposited by optional processing toproduce the article 110 of FIG. 20. The discussion involving processingto produce the article of FIGS. 12 through 15 is proper to describeproduction of the article of FIG. 20. Thus, while additional conductivematerial has been designated as a single layer (88 a/90 a) in the FIG.20 embodiment, one will understand that layer (88 a/90 a) of FIG. 20 mayrepresent any number of multiple additional layers. In subsequentembodiments, additional conductive material (88 a/90 a) will berepresented as a single layer for ease of presentation. In its formprior to combination with a conductive surface (such as surface 59 ofcells 10), the structures such as shown in FIGS. 9-15, and 16-20 can bereferred to as “current collector stock”. For the purposes of thisspecification and claims a current collector in its form prior tocombination with a conductive surface can be referred to as “currentcollector stock”. “Current collector stock” can be characterized asbeing either continuous or discrete.

The invention contemplates a particularly attractive conductive joiningthat may be achieved through a technique described herein as a laminatedcontact. In light of the teachings to follow one will recognize that thestructures shown in FIGS. 9-15 and 16-20 may function and be furthercharacterized as electrodes employing a laminated contact (laminatingelectrodes). One structure involved in the laminated contact is a firstportion of conductive structure which is to be electrically joined to asecond conductive surface. The first portion comprises a conductivepattern positioned over or embedded in a surface of an adhesive. In apreferred embodiment, the adhesive is characterized as a polymeric hotmelt adhesive. A hot melt adhesive is a material, substantially solid atroom temperature, whose full adhesive affinity is activated by heating,normally to a temperature where the material softens or meltssufficiently for it to flow under simultaneously applied pressure. Manyvarious hot melt materials, such as ethylene vinyl acetate (EVA), arewell known in the art. It is noted that while the invention is describedherein regarding the use of hot melt laminating adhesives, the inventioncontemplates use of laminating adhesives such as pressure sensitiveadhesives not requiring heat for function.

In the process of producing a laminated contact, the exposed surface ofa conductive material pattern positioned on or embedded in the surfaceof an adhesive is brought into facing relationship with a secondconductive surface to which electrical joining is intended. Heat and/orpressure are applied to soften the adhesive which then may flow aroundedges or through openings in the conductive pattern to also contact andadhesively “grab” the exposed second surface portions adjacent theconductive pattern. When heat and pressure are removed, the adhesiveadjacent edges of the conductive pattern firmly fixes features ofconductive pattern in secure mechanical contact with the second surface.

The laminated contact is particularly suitable for the electricaljoining requirements of many embodiments of the instant invention. Asimplified depiction of structure to assist understanding the concept ofa laminated contact is embodied in FIGS. 61 and 62. FIG. 61 shows a topplan view of an article 350. Article 350 comprises a conductive mesh 352positioned on the surface of or partially embedded in adhesive 351. Mesh352 may be in the form of a metal screen, a metallized fabric or afabric comprising conductive fibers and the like. Adhesive 351 possessesadhesive affinity to the conductive surface to which electrical joiningis intended. Numeral 354 indicates holes through the mesh or fabric. Onewill realize that many different patterns and conductive materials maybe suitable for the conductive material represented by conductive mesh352, including conductive comb-like patterns, serpentine traces,monolithic metal mesh patterns, metallized fabric, wires, etched or diecut metal forms, forms comprising vacuum deposited, chemically depositedand electrodeposited metals, etc.

FIG. 62 shows a sectional view of article 350 juxtaposed such that thefree surface of adhesive 351 and metal 352 are in facing relationship toa mating conductive surface 360 of article 362 to which electricaljoining is desired. In the embodiment, article 350 is seen to be acomposite of the conductive material pattern 352 positioned on a topsurface of hot melt adhesive film 351. In the embodiment, an additionalsupport film 366 is included for structural and process integrity, andpossibly barrier properties. Additional film 366 may be a polymer filmof a material such as polyethylene terephthalate, polypropylene,polycarbonate, etc. Film 366 may be multilayered and comprise layersintended to achieve functional attributes such as moisture barrier, UVprotection etc. Film 366 may also comprise a structure such as glass.Article 350 can include additional layered materials (not shown) toachieve desired functional characteristics similar to article 70discussed above. Also depicted in FIG. 62 is article 362 having a bottomsurface 360. Surface 360 may represent, for example, the top or bottomsurfaces 59 or 66 respectively of solar cell structure 10 (FIG. 2A).

In order to achieve the laminated contact, articles 350 and 362 arebrought together in the facing relationship depicted and heat andpressure are applied. The adhesive layer 351 softens and flows tocontact surface 360. In the case of the FIG. 62 embodiment, flow occursthrough the holes 354 in the mesh 352. Upon cooling and removal of thepressure, the metal mesh 352 overlays and is held in secure and firmelectrical contact with surface 360 by virtue of the adhesive bondbetween adhesive 351 and surface 360. Thus mesh may function as alaminated electrode or current collector in combination with surface360.

Figures illustrates a process 92 by which the current collector grids ofFIGS. 16 through 20 may be combined with the structure illustrated inFIG. 1A, 2A or 2B to accomplish lamination of current collectingelectrodes of top and bottom surfaces photovoltaic cell stock. Thecombining process envisioned in FIG. 21 has been demonstrated usingstandard lamination processing such as roll lamination and vacuumlamination. In a preferred embodiment, roll lamination allows continuouslamination processing and a wide choice of application temperatures andpressure. Temperatures employed are typical for lamination of standardpolymeric materials used in the high volume plastics packaging industry,normally less than about 325 degree Centigrade. Process 92 is but one ofmany processes possible to achieve such application. In FIG. 21 rolls 94and 97 represent “continuous” feed rolls of grid/buss structure on aflexible sheetlike substrate (current collector stock) as depicted inFIGS. 16 through 20. Roll 96 represents a “continuous” feed roll of thesheetlike cell stock as depicted in FIGS. 1A, 2A and 2B. FIG. 22 is asectional view taken substantially from the perspective of line 22-22 ofFIG. 21. FIG. 22 shows a photovoltaic cell 10 such as embodied in FIGS.2A and 2B disposed between two current collecting electrodes 110 a and110 b such as article 110 embodied in FIG. 20. It is understood thatsuitable insulating materials (not shown) may be applied to terminaledges 45 and 46 of cell 10 to prevent shorting by the conductivematerials of articles 110 a and 110 b in crossing the terminal edges.

FIG. 23 is a sectional view showing the article 112 resulting from usingprocess 92 to laminate the three individual structures of FIG. 22 whilesubstantially maintaining the relative positioning depicted in FIG. 22.FIG. 23 shows that a laminating current collector electrode 110 a hasnow been applied to the top conductive surface 59 of cell 10. Portionsof surface 80 a of electrode 110 a not covered with “fingers” 84 a faceand are adhesively bonded to surface 59 of cell 10. Similarly,laminating current collector electrode 110 b mates with and contacts thebottom conductive surface 66 of cell 10. Grid “fingers” 84 a of a topcurrent collector electrode 110 a project laterally across the topsurface 59 of cell stock 10 and extend to a “buss” region 86 a locatedoutside terminal edge 45 of cell stock 10. The grid “fingers” 84 a of abottom current collector electrode 110 b project laterally across thebottom surface 66 of cell stock 10 and extend to a “buss” region 86 alocated outside terminal edge 46 of cell stock 10. Thus article 112 ischaracterized as having readily accessible conductive surface portions114 and 116 in the form of tabs in electrical communication with bothtop cell surface 59 and bottom cell surface 66 respectively. Article 112can be described as a “tabbed cell stock”. In the present specificationand claims, a “tabbed cell stock” is defined as a photovoltaic cellstructure combined with electrically conducting material in electricalcommunication with a conductive surface of the cell structure, andfurther wherein the electrically conducting material extends outside aterminal edge of the cell structure to present a readily accessiblecontact surface. In light of the present teachings, one will understandthat “tabbed cell stock” can be characterized as being either continuousor discrete. One will also recognize that electrodes 110 a and 110 b canbe used independently of each other. For example, 110 b could beemployed as a back side electrode while a current collector structurallyor materially different than 110 b is employed on the top side of cell10. Also, one will understand that while electrodes 110 a and 110 b areshown in the embodiment to be the same structure, different structuresand materials may be chosen for electrodes 110 a and 110 b.

A “tabbed cell stock” combination 112 has a number of fundamentaladvantageous attributes. First, the laminated current collectorelectrodes protect the surfaces of the cell from defects possiblyintroduced by the further handing associated with finalinterconnections. Moreover, “tabbed cell stock” can be produced as acontinuous form using a continuous cell “strip” originally produced inthe “machine” direction (“Y” direction of FIG. 1 or 1A). Such acontinuous raw cell “strip” would be anticipated to have more uniformperformance characteristics than portions chosen transverse to the“machine” direction (“X” direction of FIG. 1). Next, the “tabbed cellstock” combination 112 may be produced in a continuous fashion in the Ydirection (direction normal to the paper in the sectional view of FIG.23) using either roll lamination or intermittent vacuum lamination.Following the envisioned lamination, the “tabbed cell stock” strip canbe continuously monitored for quality since there is ready access to theconductive, exposed free surfaces 114 and 116 in electricalcommunication with top cell surface 59 and the cell bottom surface 66respectively. Alternative “sorting” options exist at this point.

a. It would be anticipated that since the raw cell “strip” is continuousin the “machine” direction, performance variation would be minimized andthe “tabbed cell stock” could be accumulated in takeup roll form.

b. Should there be excessive performance variation along the length ofthe raw cell “strip”, the “tabbed cell stock” combination may becontinuously characterized, cut to standard lengths and automaticallysorted prior to assembly into a module. Excessively defective cellmaterial could be readily identified and discarded prior to finalinterconnection into a module. Acceptable lengths could be automaticallysorted according to defined parameters and placed in appropriatecassette feeders prior to assembly into final modules.

The lamination process 92 of FIG. 21 normally involves application ofheat and pressure. Temperatures will vary depending on materials andexposure time. Typical temperatures less than about 325 degreeCentigrade are envisioned. Lamination temperatures of less than 325degree centigrade would be more than sufficient to melt and activate notonly typical polymeric sealing materials but also many low melting pointmetals, alloys and metallic solders. For example, tin melts at about 230degree Centigrade and its alloys even lower. Tin alloys with for examplebismuth, lead and indium are common industrial materials. Manyconductive “hot melt” adhesives can be activated at even lowertemperatures such as 200 degree Centigrade. Typical thermal curingtemperatures for polymers are in the range 95 to 200 degree Centigrade.Thus, typical lamination practice widespread in the packaging industryis normally appropriate to simultaneously accomplish many conductivejoining possibilities.

It will be understood that while the process 92 of FIG. 21 envisions aroll type lamination, other forms of laminating process are appropriatein practice of the invention. For example, a semi-continuous or indexedfeed lamination process, perhaps augmented by vacuum, may be employed.Moreover, should the substrate 70 a comprise a rigid or discretecomponent such as glass, a semi-continuous or discrete batch laminationprocess may be envisioned.

The sectional drawings of FIGS. 24 and 25 show the result of joiningmultiple articles 112 a, 112 b. Each article has a readily accessibledownward facing pattern 114 (in the drawing perspective) with aconductive surface 100 a in communication with the cell top surface 59.A readily accessible upward facing pattern 116 having another conductivesurface 100 a communicates with the cell bottom surfaces 66. One willappreciate that in this embodiment, current collector 110 b functions asan interconnecting substrate unit. Series connections are easilyachieved by overlapping the top surface extension 114 of one article 112b and a bottom surface extension 116 of a second article 112 a andelectrically connecting these extensions with electrically conductivejoining means such as conductive adhesive 42 shown in FIGS. 24 and 25.Other electrically conductive joining means including those definedabove may be selected in place of conductive adhesive 42. For example,surfaces 114 and 116 could comprise solderable material which would fuseduring a lamination process. Alternatively, surfaces 114 and 116 couldoverlap and be electrically joined to top and bottom surfaces of a metalfoil member. Finally, since the articles 112 of FIG. 23 can be producedin a continuous form (in the direction normal to the paper in FIG. 23)the series connections and array production embodied in FIGS. 24 and 25may also be accomplished in a continuous manner by using continuous feedrolls of “tabbed cell stock” 112. However, while continuous assembly maybe possible, other processing may be envisioned to produce theinterconnection embodied in FIGS. 24 and 25. For example, definedlengths of “tabbed cell stock” 112 could be produced by subdividing acontinuous strip of “tabbed cell stock” 112 in the Y dimension and theindividual articles thereby produced could be arranged as shown in FIGS.24 and 25 using, for example, standard pick and place positioning.

FIG. 26 is a top plan view of an article in production of anotherembodiment of a laminating current collector grid or electrode accordingto the instant invention. FIG. 26 embodies a polymer based film or glasssubstrate 120. Substrate 120 has width X-120 and length Y120. Inembodiments, taught in detail below, Y-120 may be much greater thanwidth X-120, whereby film 120 can generally be described as “continuous”in length and able to be processed in length direction Y-120 in acontinuous roll-to-roll fashion. FIG. 27 is a sectional view takensubstantially from the view 27-27 of FIG. 26. Thickness dimension Z-120is small in comparison to dimensions Y-120, X-120 and thus substrate 120may have a flexible sheetlike, or web structure contributing to possibleroll-to-roll processing. As shown in FIG. 27, substrate 120 may be alaminate of multiple layers 72 b, 74 b, 76 b etc. or may comprise asingle layer of material. Thus substrate 120 may have structure similarto that of the FIGS. 6 through 8 embodiments, and the discussion of thecharacteristics of article 70 of FIGS. 6 through 8 is proper tocharacterize article 120 as well. As with the representation of thearticle 70 of FIGS. 6 through 8, and as shown in FIG. 28, article 120(possibly multilayered) will be embodied as a single layer in thefollowing for simplicity of presentation.

FIG. 29 is a top plan view of an article 124 following an additionalprocessing step using article 120. FIG. 30 is a sectional viewsubstantially from the perspective of lines 30-30 of FIG. 29. Thestructure depicted in FIGS. 29 and 30 is similar to that embodied inFIGS. 16 and 18. It is seen that article 124 comprises a pattern of“fingers” or “traces”, designated 84 b, extending from “buss” or “tab”structures, designated 86 b. In the embodiments of FIGS. 29 and 30, both“fingers” 84 b and “busses” 86 b are positioned on supporting substrate120 in a grid pattern. “Fingers” 84 b extend in the width X-124direction of article 124 and “busses” (“tabs”) 86 b extend in the Y-124direction substantially perpendicular to the “fingers”. In the FIG. 29embodiment, it is seen that the ends of the fingers opposite the “buss”86 b are joined by connecting trace of material 128 extending in the“Y-124” direction. In the embodiment of FIGS. 29 and 30, the buss 86 bregion is characterized as having multiple regions 126 devoid ofmaterial forming “buss” pattern 86 b. In the FIG. 29 embodiment, thevoided regions 126 are presented as circular regions periodically spacedin the “Y-124” direction. One will understand in light of the teachingsto follow that the circular forms 126 depicted in FIG. 29 is but one ofmany different patterns possible for the voided regions 126. Thesectional view of FIG. 30 shows the voided regions 126 leave regions ofthe top surface 80 b of substrate 120 exposed. Surface 80 b of substrate120 remains exposed in those regions not covered by the finger/busspattern. These exposed regions are further indicated by numeral 127 inFIG. 29.

Structure 124 may be produced, processed and extend continuously in thelength “Y-124” direction.

The embodiment of FIGS. 29 and 30 show substrate 120 as a uniformmonolithic structure. As discussed for the embodiments of FIGS. 9-15 and16-20, regions of substrate 120 associated with fingers 84 b may differfrom regions supporting buss 86 b. However, it is understood that shouldarticle 124 be intended to mate with a light incident surface 59 of aphotovoltaic cell, portions of substrate 120 not overlayed by materialforming “fingers” 84 b will remain transparent or translucent to visiblelight. Such regions are generally identified by numeral 127 in FIG. 29.In the embodiment of FIGS. 29 and 30, the “fingers” 84 b and “busses” 86b are shown to be a single layer for simplicity of presentation.However, the “fingers” and “busses” can comprise multiple layers ofdiffering materials chosen to support various functional attributes. Forexample the material defining the “buss” or “finger” patterns which isin direct contact with substrate 120 may be chosen for its adhesiveaffinity to surface 80 b of substrate 120 and also to a subsequentlyapplied constituent of the buss or finger structure. Further, it may beadvantageous to have the first visible material component of the fingersand busses be of dark color or black. As will be shown, the lightincident side (outside surface) of the substrate 120 will eventually besurface 82 b. By having the first visible component of the fingers andbusses be dark, they will aesthetically blend with the generally darkcolor of the photovoltaic cell. This eliminates the often objectionableappearance of a metal colored grid pattern. As previously discussedpermissible dimensions and structure for the “fingers” and “busses” willvary somewhat depending on materials and fabrication process used forthe fingers and busses, and the dimensions of the individual cell.

“Fingers” 84 b and “busses” 86 b may comprise electrically conductivematerial. Examples of such materials are metal wires and foils, stampedmetal patterns, conductive metal containing inks and pastes such asthose having a conductive filler comprising silver or stainless steel,patterned deposited metals such as etched metal patterns or maskedvacuum deposited metals, intrinsically conductive polymers and DERformulations. In a preferred embodiment, the “fingers” and “busses”comprise electroplateable material such as DER or an electricallyconductive ink which will enhance or allow subsequent metalelectrodeposition. “Fingers” 84 b and “busses” 86 b may also comprisenon-conductive material which would assist accomplishing a subsequentdeposition of conductive material in the pattern defined by the“fingers” and “busses”. For example, “fingers” 84 b or “busses” 86 bcould comprise a polymer which may be seeded to catalyze chemicaldeposition of a metal in a subsequent step. An example of such amaterial is seeded ABS. Patterns comprising electroplateable materialsor materials facilitating subsequent electrodeposition are oftenreferred to as “seed” patterns or layers. “Fingers” 84 b and “busses” 86b may also comprise materials selected to promote adhesion of asubsequently applied conductive material. “Fingers” 84 b and “busses” 86b may differ in actual composition and be applied separately. Forexample, “fingers” 84 b may comprise a conductive ink while “buss/tab”86 b may comprise a conductive metal foil strip. Alternatively, fingersand busses may comprise a continuous unvarying monolithic materialstructure forming portions of both fingers and busses. Fingers andbusses need not both be present in certain embodiments of the invention.

The embodiments of FIGS. 29 and 30 show the “fingers” 84 b, “busses” 86b, and connecting trace 128 as essentially planar rectangularstructures. Other geometrical forms are clearly possible, especiallywhen design flexibility is associated with the process used to establishthe material pattern of “fingers” and “busses”. “Design flexible”processing includes printing of conductive inks or “seed” layers, foiletching or stamping, masked deposition using paint or vacuum deposition,and the like. For example, these conductive paths can have triangulartype surface structures increasing in width (and thus cross section) inthe direction of current flow. Thus the resistance decreases as netcurrent accumulates to reduce power losses. Alternatively, one mayselect more intricate patterns, such as a “watershed” pattern asdescribed in U.S. Patent Application Publication 2006/0157103 A1 whichis hereby incorporated in its entirety by reference. Various structuralfeatures, such as radiused connections between fingers and busses may beemployed to improve structural robustness.

It is important to note however that the laminating current collectorstructures of the instant invention may be manufactured utilizingcontinuous, bulk roll to roll processing. While the collector gridembodiments of the current invention may advantageously be producedusing continuous processing, one will recognize that combining of gridsor electrodes so produced with mating conductive surfaces may beaccomplished using either continuous or batch processing. In one case itmay be desired to produce photovoltaic cells having discrete defineddimensions. For example, single crystal silicon cells are often producedhaving X-Y dimensions of 6 inches by 6 inches. In this case thecollector grids of the instant invention, which may be producedcontinuously, may then be subdivided to dimensions appropriate forcombining with such cells. In other cases, such as production of manythin film photovoltaic structures, a continuous roll-to-roll productionof an expansive surface article can be accomplished in the “Y” directionas identified in FIG. 1. Such a continuous expansive photovoltaicstructure may be combined with a continuous arrangement of collectorgrids of the instant invention in a semicontinuous or continuous manner.Alternatively the expansive semiconductor structure may be subdividedinto continuous strips of cell stock. In this case, combining acontinuous strip of cell stock with a continuous strip of collector gridof the instant invention may be accomplished in a continuous orsemi-continuous manner.

FIG. 31 corresponds to the view of FIG. 30 following an additionaloptional processing step. The FIG. 31 article is now designated bynumeral 125 to reflect this additional processing. FIG. 31 showsadditional conductive material deposited onto the “fingers” 84 b and“buss” 86 b. In this embodiment additional conductive material isdesignated by one or more layers (88 b/90 b) and the fingers and bussesproject above surface 80 b as shown by dimension “H”. It is understoodthat conductive material could comprise more than two layers or be asingle layer. Conductive material (88 b/90 b) is shown as a single layerin the FIG. 31 embodiment for ease of presentation. Article 125 isanother embodiment of a “current collector stock”. Dimension “H” isnormally smaller than about 50 micrometers and thus the structure offingers and busses depicted in FIG. 31 can be considered as a “lowprofile” structure. In some cases it may be desirable to reduce theheight of projection “H” prior to eventual combination with a conductivesurface such as 59 or 66 of photovoltaic cell 10. This reduction may beaccomplished by passing the structures as depicted in FIGS. 29-31through a pressurized and/or heated roller or the like to partiallyembed “fingers” 84 b and/or “busses” 86 b into layer 72 b of substrate120.

While each additional conductive material is shown the FIG. 31embodiment as having the same continuous monolithic material extendingover both the buss and finger patterns, one will realize that selectivedeposition techniques would allow the additional “finger” layers todiffer from additional “buss” layers. For example, as shown in FIG. 31,“fingers” 84 b have top free surface 98 b and “busses” 86 b have topfree surface 100 b. As noted, selective deposition techniques such asbrush electroplating or masked deposition would allow differentmaterials to be considered for the “buss” surface 100 b and “finger”surface 98 b. In a preferred embodiment, at least one of the additionallayers (88 b/90 b) etc. are deposited by electrodeposition, takingadvantage of the deposition speed, compositional choice, low cost andselectivity of the electrodeposition process. Many various metals,including highly conductive silver, copper and gold, nickel, tin andalloys can be readily electrodeposited. In these embodiments, it may beadvantageous to utilize electrodeposition technology giving anelectrodeposit of low tensile stress to prevent curling and promoteflatness of the metal deposits. In particular, use of nickel depositedfrom a nickel sulfamate bath, nickel deposited from a bath containingstress reducing additives such as brighteners, or copper from a standardacid copper bath have been found particularly suitable.Electrodeposition also permits precise control of thickness andcomposition to permit optimization of other requirements of the overallmanufacturing process for interconnected arrays. Alternatively, theseadditional conductive layers may be deposited by selective chemicaldeposition or registered masked vapor deposition. These additionallayers (88/90) may also comprise conductive inks applied by registeredprinting.

It has been found very advantageous to form surface 98 b of “fingers” 84b or top surface 100 b of “busses” 86 b with a material compatible withthe conductive surface with which eventual contact is made. In preferredembodiments, electroless deposition or electrodeposition is used to forma suitable surface 98 b or 100 b. Specifically electrodeposition offersa wide choice of potentially suitable materials to form these topsurfaces. Corrosion resistant materials such as nickel, chromium, tin,indium, silver, gold and platinum are readily electrodeposited. Whencompatible, of course, surfaces comprising metals such as copper or zincor alloys of copper or zinc may be considered. Alternatively, thesurface 98 b or 100 b may comprise a conductive conversion coating, suchas a chromate coating, of a material such as copper or zinc. Further, aswill be discussed below, it may be highly advantageous to choose amaterial to form surfaces 98 b or 100 b which exhibits adhesive orbonding ability to a subsequently positioned abutting conductivesurface. For example, it may be advantageous to form surfaces 98 b and100 b using an electrically conductive adhesive or low melting pointmetal or solder. For example, forming surfaces 98 b or 100 b with aconductive hot melt adhesive or with materials such as tin or tinalloyed with element such as lead, bismuth or indium could result in asurface material having a melting point less than the temperature of asubsequent lamination process. This would facilitate electrical joiningduring the subsequent lamination steps. One will note that materialsforming “fingers” surface 98 b and “buss” surface 100 b need not be thesame.

FIG. 32 depicts an arrangement of 3 articles just prior to a laminatingprocess according to a process embodiment such as that of FIG. 21. Inthe FIG. 32 embodiment, “current collector stock” 125 is positionedabove a photovoltaic cell 10. A second article of laminating “currentcollector stock”, identified by numeral 129, is positioned beneath cell10. Article 129 may be similar in structure to article 110 of FIG. 20.

FIG. 33 shows the article 130 resulting from passing the FIG. 32arrangement through a lamination process as depicted in FIG. 21. Thelamination process has applied article 125 over the top surface 59 ofcell 10. Thus, the conductive surfaces 98 b of grid “fingers” 84 b ofarticle 125 are fixed by the lamination in intimate contact withconductive top surface 59 of cell 10. The lamination process hassimilarly positioned the conductive surface 98 a of “fingers” 84 a ofarticle 129 in intimate contact with the bottom surface 66 of cell 10.The conductive material associated with current collector stock 125extends past a first terminal edge 46 of cell 10. The conductivematerial associated with current collector stock 129 extends past secondterminal edge 45 of cell 10. These extensions, identified by numerals134 and 136 in FIG. 33, form convenient “tab” surfaces to facilitateelectrical connections to and from the actual cell. Thus article 130 canbe properly characterized as a form or embodiment of a “tabbed cellstock”.

FIG. 34 embodies the combination of multiple portions of “tabbed cellstock” 130. In the FIG. 34 embodiment, an extension 134 a associatedwith a first unit of “tabbed cell stock” 130 a overlaps extension 136 bof an adjacent unit of “tabbed cell stock” 130 b. The same spatialarrangement exists between “tabbed cell stock” units 130 b and 130 c.The conductive surfaces associated with the mating extensions arepositioned and held in secure contact as a result of an adhesivematerial forming surface 80 b of the substrate 120 melting and fillingholes shown at 126. The mating contact is additionally secured byadhesive bonding produced by additional originally exposed portions ofthe substrates, shown at 127, in the region of the mechanical andpressure induced electrical joining between adjacent units of “tabbedcell stock”. These originally exposed regions of substrate surface inthe region of the mechanical and pressure induced electrical joiningbetween adjacent units of “tabbed cell stock” are identified by thenumeral 127 in the FIG. 34. It is clear that in the FIG. 34 embodiment asecure and robust series electrical connection is achieved betweenadjacent units of “tabbed cell stock” by virtue of the laminationprocess taught herein.

Referring now to FIGS. 35 through 38, there are shown embodiments of astarting structure for another grid/interconnect article of theinvention. FIG. 35 is a top plan view of an article 198. Article 198comprises a polymeric film or glass sheet substrate generally identifiedby numeral 200. Substrate 200 has width X-200 and length Y-200. LengthY-200 is sometimes much greater the width X-200 such that film 200 canbe processed in essentially a “roll-to-roll” fashion. However, this isnot necessarily the case. Dimension “Y” can be chosen according to theapplication and process envisioned. FIG. 36 is a sectional view takensubstantially from the perspective of lines 36-36 of FIG. 35. Thicknessdimension Z-200 is normally small in comparison to dimensions Y-200 andX-200 and thus substrate 200 has a sheetlike structure and is oftenflexible. Substrate 200 is further characterized by having regions ofessentially solid structure combined with regions having holes 202extending through the thickness Z-200. In the FIG. 35 embodiment, asubstantially solid region is generally defined by a width Wcc,representing a current collection portion. Another portion withthrough-holes (holey region) is generally defined by width Win,representing an interconnection region. Imaginary line 201 separates thetwo portions. Holes 202 may be formed by simple punching, laser drillingand the like. Alternatively, holey region Win may comprise a fabricjoined to region Wcc along imaginary line 201, whereby the fabricstructure comprises through-holes. The reason for these distinctions anddefinitions will become clear in light of the following teachings.

Referring now to FIG. 36, region Wcc of substrate 200 has a firstsurface 210 and second surface 212. The sectional view of substrate 200shown in FIG. 36 shows a single layer structure. This depiction issuitable for simplicity and clarity of presentation. Often, however,film 200 will comprise a laminate of multiple layers as depicted in FIG.37. In the FIG. 37 embodiment, substrate 200 is seen to comprisemultiple layers 204, 206, 208, etc. As previously taught herein, themultiple layers may comprise inorganic or organic components such asthermoplastics, thermosets, or silicon containing glass-like layers. Thevarious layers are intended to supply functional attributes such asenvironmental barrier protection or adhesive characteristics. Inparticular, in light of the teachings herein, one will recognize that itmay be advantageous to have layer 204 forming surface 210 comprise asealing material such as ethylene vinyl acetate (EVA), an ionomer, anolefin based adhesive, atactic polyolefin, or a polymer containing polarfunctional groups for adhesive characteristics during a possiblesubsequent lamination process. For example, the invention has beensuccessfully demonstrated using a standard laminating material sold byGBC Corp., Northbrook, Ill., 60062. Additional layers 206, 208 etc. maycomprise materials which assist in support or processing such aspolypropylene and polyethylene terepthalate, barrier materials such asfluorinated polymers and biaxially oriented polypropylene, and materialsoffering protection against ultraviolet radiation as previously taughtin characterizing substrate 70 of FIG. 6.

As embodied in FIGS. 35 and 36, the solid regions Wcc and “holey”regions Win of substrate 200 may comprise the same material. This is notnecessarily the case. For example, the “holey” regions Win of substrate200 could comprise a fabric, woven or non-woven, joined to an adjacentsubstantially solid region along imaginary line 201. However, shouldsubstrate 200 be used for current collection from a light incidentsurface of a photovoltaic cell, the materials forming the solid regionWcc should be relatively transparent or translucent to visible light, aswill be understood in light of the teachings to follow.

FIG. 38 depicts an embodiment wherein multiple widths 200-1, 200-2 etc.of the general structure of FIGS. 35 and 36 are joined together in agenerally repetitive pattern in the width direction. Such a structureallows simultaneous production of multiple repeat structurescorresponding to widths 200-1, 200-2 in a fashion similar to that taughtin conjunction with the embodiments of FIGS. 6 through 15.

FIG. 39 is a plan view of the FIG. 35 substrate 200 following anadditional processing step, and FIG. 40 is a sectional view taken alongline 40-40 of FIG. 39. In FIGS. 39 and 40, the article is now designatedby the numeral 214 to reflect this additional processing. In FIGS. 39and 40, it is seen that a pattern of “fingers” 216 has been formed bymaterial 218 positioned in a pattern over surface 210 of originalsheetlike substrate 200. “Fingers” 216 extend over the width Wcc of thesolid portion of sheetlike structure 214. The “fingers” 216 extend tothe “holey” interconnection region generally defined by Win. Portions ofthe Wcc region not overlayed by “fingers” 216 remain transparent ortranslucent to visible light. The “fingers” may comprise electricallyconductive material. Examples of such materials are metal containinginks, patterned deposited metals such as etched metal patterns, stampedmetal patterns, masked vacuum deposited metal patterns, fine metalwires, intrinsically conductive polymers and DER formulations. In otherembodiments the “fingers” may comprise materials intended to facilitatesubsequent deposition of conductive material in the pattern defined bythe fingers. An example of such a material would be ABS, catalyzed toconstitute a “seed” layer to initiate chemical “electroless” metaldeposition. Another example would be a material functioning to promoteadhesion of a subsequently applied conductive material to the film 200.In a preferred embodiment, the “fingers” comprise material which willenhance or allow subsequent metal electrodeposition such as a DER orelectrically conductive ink. In the embodiment of FIGS. 39 and 40, the“fingers” 216 are shown to be a single layer of material 218 forsimplicity of presentation. However, the “fingers” can comprise multiplelayers of differing materials chosen to support various functionalattributes as has previously been taught.

Continuing reference to FIGS. 39 and 40 also shows additional material220 applied to the “holey” region Win of article 214 and extendingthrough holes 202 from surface 210 to surface 212. As with the materialcomprising the “fingers” 216, the material 220 applied to the “holey”region Win is either conductive or material intended to facilitatesubsequent deposition of conductive material. One will understand that“holey” region Win may comprise a fabric which may further compriseconductive material extending through the natural holes of the fabric.Further, such a fabric may comprise fibrils formed from conductivematerials such as metals or conductive polymers. Such a fabric structurecan be expected to increase and retain flexibility after subsequentprocessing such as metal electroplating, and perhaps bonding ability ofthe ultimate interconnected cells. Alternatively one may choose toestablish electrical communication between surface 210 and 212 by usingan electrically conductive polymer or metal foil to form portions of thesubstrate associated with interconnection region Win as will beunderstood in light of the teachings contained hereafter. In theembodiment of FIGS. 39 and 40, the “holey” region takes the general formof a “buss” 221 extending in the Y-214 direction in communication withthe individual fingers. However, as one will understand through thesubsequent teachings, the invention requires only that conductivecommunication extend from the fingers to a region Win intended to beelectrically joined to the bottom conductive surface of an adjacentcell. The “holey” region Win thus does not require overall electricalcontinuity in the “Y” direction as is characteristic of a “buss” formdepicted in the embodiment of FIGS. 39 and 40.

Reference to FIG. 40 shows that the material 220 applied to the “holey”interconnection region Win is shown as the same as that applied to formthe fingers 216. However, these materials 218 and 220 need not beidentical. In this embodiment material 220 applied to the “holey” regionextends through holes 202 and onto the opposite second surface 212 ofarticle 214. The extension of material 220 through the holes 202 can bereadily accomplished as a result of the relatively small thickness (Zdimension) of the sheetlike substrate 200. Techniques include two sidedprinting of material 220, through hole spray application, maskedmetallization or selective chemical deposition or mechanical means suchas stapling, wire sewing or riveting.

FIG. 41 is a view similar to that of FIG. 40 following an additionaloptional processing step. The article embodied in FIG. 41 is designatedby numeral 226 to reflect this additional processing. It is seen in FIG.41 that the additional processing has deposited highly conductivematerial 222 over the originally free surfaces of materials 218 and 220.Material 222 normally comprises metal-based material such as copper ornickel, tin or a conductive metal containing paste or ink. Typicaldeposition techniques such as printing, chemical or electrochemicalmetal deposition and masked deposition can be used for this additionaloptional process to produce the article 226. In a preferred embodiment,electrodeposition is chosen for its speed, ease, and cost effectivenessas taught above. It is understood that article 226 is another embodimentof “current collector stock”.

It is seen in FIG. 41 that highly conductive material 222 extendsthrough holes to electrically join and form electrically conductivesurfaces on opposite sides of article 226. While shown as a single layerin the FIG. 41 embodiment, the highly conductive material can comprisemultiple layers to achieve functional value. In particular, a layer ofcopper is often desirable for its high conductivity. Nickel is oftendesired for its adhesion characteristics, plateability and corrosionresistance. The exposed surface 229 of material 222 can be selected forcorrosion resistance and bonding ability. It has been found veryadvantageous to form surface 229 with a material compatible with theconductive surface with which eventual contact is made. In preferredembodiments, electroless deposition or electrodeposition is used to forma suitable metallic surface. Specifically electrodeposition offers awide choice of potentially suitable materials to form the top surface229. Corrosion resistant materials such as nickel, chromium, tin,indium, silver, gold and platinum are readily electrodeposited may bechosen to form surface 229. When compatible, of course, surfacescomprising metals such as copper or zinc or alloys of copper or zinc maybe considered. Alternatively, the surface 229 may comprise a conductiveconversion coating, such as a chromate coating, of a material such ascopper or zinc. Further, it may be highly advantageous to choose amaterial, such as a conductive adhesive or metallic solder to formsurface 229 which exhibits adhesive or bonding ability to a subsequentlypositioned abutting conductive surface. In this regard,electrodeposition offers a wide choice of materials to form surface 229.In particular, indium, tin or tin containing alloys are a possiblechoice of material to form the exposed surface 229 of material 222.These metals melt at relatively low temperatures less than about 275degree Centigrade. Thus these metals may be desirable to promote ohmicjoining, through soldering, to other components in subsequent processingsuch as lamination. Alternatively, exposed surface 229 may comprise anelectrically conductive adhesive. Selective deposition techniques suchas brush plating or printing would allow the conductive materials ofregion Win to differ from those of fingers 216. In addition to supplyingelectrical communication from surfaces 210 to 212, holes 202 alsofunction to increase flexibility of “buss” 221 by relieving the“sandwiching” effect of continuous oppositely disposed layers. Holes 202can clearly be the holes naturally present should substrate 200 in theregion Win be a fabric. One realizes that an important attribute of theembodied structure is that electrical communication is achieved betweenopposing surfaces 210 and 212 of substrate 200 in the interconnectionregion Win. One further realizes that this communication may be achievedusing structure other than using the holes shown. For example, similarcommunication by be achieved by using a conductive fabric, metal mesh,an electrically conductive polymer or metal foil to form a portion ofthe substrate 200 associated with region Win. These alternate materialswould be patched to the remaining transparent current collector portionWcc of substrate 200. In all these ways electrical communication isachieved from surface 200 to opposite surface 210 within region Win.

One method of combining the current collector stock 226 embodied in FIG.41 with a cell stock 10 as embodied in FIGS. 1A and 2A is illustrated inFIGS. 42 and 43. In the FIG. 43 structure, individual current collectorstocks 226 are combined with cells 10 a, 10 b, 10 c respectively toproduce a series interconnected array. This may be accomplished via aprocess generally described as follows.

As embodied in FIG. 42, individual current collector stock, such as 226,is combined with cells such as 10 by positioning of surface region “Wcc”of current collector stock 226 having free surface 210 in registrationwith the light incident surface 59 of cell 10. The article so producedis identified as article 227. Adhesion joining the two surfaces isaccomplished by a suitable process. In particular, the material formingthe remaining free surface 210 of article 226 (that portion of surface210 not covered with conductive material 222) may be a sealing materialchosen for adhesive affinity to surface 59 of cell 10 thereby promotinggood adhesion between the collector stock 226 and cell surface 59resulting from a laminating process such as that depicted in FIG. 21.Such a laminating process brings the conductive material of fingers 216into firm and effective contact with the window electrode 18 formingsurface 59 of cell 10. This contact is ensured by the blanketing “holddown” afforded by the adhesive bonding adjacent the conductive fingers216. Also, as mentioned above, the nature of the free surface ofconductive material 222 may optionally be manipulated and chosen tofurther enhance ohmic joining and adhesion. It is envisioned that batchor continuous laminating would be suitable. The invention has beendemonstrated using both roll laminators and batch vacuum laminators.Should the articles 226 and 10 be in a continuous form it will beunderstood that article 227 could be formed as a continuous “tabbed cellstock.” The subsequent series arrangement of articles 227 a, 227 b,depicted in FIG. 43 may employ strip portions of “tabbed cell stock”having a defined length. Alternatively continuous series interconnectionof multiple strips of tabbed cell stock supplied from correspondingmultiple rolls of tabbed cell stock is possible.

Referring to FIG. 43, it is seen that proper positioning allows theconductive material 222 extending over the second surface 212 of article227 b to be ohmicly adhered to the bottom surface 66 of cell 10 a. Thisjoining is accomplished by suitable electrical joining techniques suchas soldering, riveting, spot welding or conductive adhesive application.The particular ohmic joining technique embodied in FIG. 43 is throughelectrically conductive adhesive 42. A particularly suitable conductiveadhesive is one comprising a carbon black filler in a polymer matrixpossibly augmented with a more highly conductive metal filler. Suchadhesive formulations are relatively inexpensive and can be produced ashot melt formulations. Despite the fact that adhesive formulationsemploying carbon black alone have relatively high intrinsicresistivities (of the order 1 ohm-cm.), the bonding in this embodimentis accomplished through a relatively thin adhesive layer and over abroad surface. Thus the resulting resistance losses are relativelylimited. A hot melt conductive adhesive is very suitable forestablishing the ohmic connection using a straightforward laminationprocess.

FIG. 43 embodies multiple cells assembled in a series arrangement usingthe teachings of the instant invention. In FIG. 43, “i” indicates thedirection of net current flow and “hv” indicates the light incidence forthe arrangement. It is noted that the arrangement of FIG. 43 resembles ashingling arrangement of cells, but with an important distinction. Theprior art shingling arrangements have included an overlapping of cellsat a sacrifice of portions of very valuable cell surface. In the FIG. 43teaching, the benefits of the shingling interconnection concept areachieved without any loss of photovoltaic surface from shading by anoverlapping cell. In addition, the FIG. 43 arrangement retains a highdegree of flexibility because there is no immediate overlap of the metalfoil cell substrate. Conversely, inspection of the FIG. 43 embodimentshows that interconnection may also be achieved without any substantialseparation between adjacent connected cells (except for a very slight,vertical displacement). In this way active collection area is maximized,since no “dead area” exists between cells.

Yet another form of the instant invention is embodied in FIGS. 44through 56. FIG. 44 is a top plan view of an article designated 230.Article 230 has width “X-230” and length “Y-230”. It is contemplatedthat “Y-230” may be considerably greater than “X-230” such that article230 may be processed in continuous roll-to-roll fashion. However, suchcontinuous processing is not a requirement.

FIG. 45 is a sectional view taken substantially from the perspective oflines 45-45 of FIG. 44. It is shown in FIG. 45 that article 230 maycomprise any number of layers such as those designated by numerals 232,234, 236. The layers are intended to supply functional attributes toarticle 230 as has been discussed for prior embodiments. Article 230 isalso shown to have thickness “Z-230”. “Z-230” is much smaller than“X-230” of “Y-230” and thus article 230 may be generally characterizedas being flexible and sheetlike. Article 230 is shown to have a firstsurface 238 and second surface 240. As will become clear in subsequentembodiments, it may be advantageous to form layer 232 forming surface238 using a material having adhesive affinity to the bottom surface 66of cell 10. In addition, it may be advantageous to have surface 240formed by a material having adhesive affinity to surface 59 of cell 10.

FIG. 46 is an alternate sectional embodiment depicting an article 230 a.The layers forming article 230 a do not necessarily have to cover theentire expanse of article 230 a.

FIG. 47 is a simplified sectional view of the article 230 which will beused to simplify presentation of embodiments to follow. While FIG. 47presents article 230 as a single layer, it is emphasized that article230 may comprise any number of layers.

FIG. 48 is a top plan view of the initial article 230 following anadditional processing step. The article embodied in FIG. 48 isdesignated 244 to reflect this additional processing step. FIG. 49 is asectional view taken substantially from the perspective of lines 49-49of FIG. 48. Reference to FIGS. 48 and 49 show that the additionalprocessing has produced holes 242 in the direction of “Y-244”. The holesextend from the top surface 238 to the bottom surface 240 of article244. Holes 242 may be produced by any number of techniques such as laserdrilling or simple punching.

FIG. 50 is a top plan view of the article 244 following an additionalprocessing step. The article of FIG. 50 is designated 250 to reflectthis additional processing. FIG. 51 is a sectional view takensubstantially from the perspective of lines 51-51 of FIG. 50. Referenceto FIGS. 50 and 51 shows that material 251 has been applied to the firstsurface 238 in the form of “fingers” 252. Further, material 253 has beenapplied to second surface 240 in the form of “fingers” 254. In theembodiment, “fingers” 252 and 254 extend substantially perpendicularfrom a “buss-like” structure 256 extending in the direction “Y-250”. Asseen in FIG. 51, additional materials 251 and 253 extend through theholes 242. In the FIG. 51 embodiment, materials 251 and 253 are shown asbeing the same. This is not necessarily a requirement and they may bedifferent. Also, in the embodiment of FIGS. 50 and 51, the buss-likestructure 256 is shown as being formed by materials 251/253. This is notnecessarily a requirement. Materials forming the “fingers” 252 and 254and “buss” 256 may all be the same or they may differ in actualcomposition and be applied separately. Alternatively, fingers and bussesmay comprise a continuous monolithic material structure forming portionsof both fingers and busses. Fingers and busses need not both be presentin certain embodiments of the invention.

As in prior embodiments, “fingers” 252 and 254 and “buss” 256 maycomprise electrically conductive material. Examples of such materialsare metal wires and metal foils, conductive metal containing inks andpastes, patterned metals such as etched metal patterns or masked vacuumdeposited metals, intrinsically conductive polymers, conductive inks andDER formulations. In a preferred embodiment, the “fingers” and “busses”comprise material such as DER or an electrically conductive ink such assilver containing ink which will enhance or allow subsequent metalelectrodeposition. “Fingers” 252 and 254 and “buss” 256 may alsocomprise non-conductive material which would assist accomplishing asubsequent deposition of conductive material in the pattern defined bythe “fingers” and “busses”. For example, “fingers” 252 and 254 or “buss”256 could comprise a polymer which may be seeded to catalyze chemicaldeposition of a metal in a subsequent step. An example of such amaterial is “seeded” ABS. “Fingers” 252 and 254 and “buss” 256 may alsocomprise materials selected to promote adhesion of a subsequentlyapplied conductive material.

FIG. 52 is a sectional view showing the article 250 following anadditional optional processing step. The article of FIG. 52 isdesignated 260 to reflect this additional processing. In a fashion likethat described above for production of prior embodiments of currentcollector structures, additional conductive material 266 has beendeposited by optional processing to produce the article 260 of FIG. 52.The discussion involving processing to produce the articles of FIGS.12-15, 20, 31, and 41 is proper to describe the additional processing toproduce the article 260 of FIG. 52. In a preferred embodiment,conductive material 266 comprises material applied by chemical metaldeposition or metal electrodeposition. In addition, while shown in FIG.52 as a single continuous, monolithic layer, the additional conductivematerial may comprise multiple layers. As in prior embodiments, it maybe advantageous to use a material such as a low melting point alloy orconductive adhesive to form exterior surface 268 of additionalconductive material 266. Additional conductive material overlaying“fingers” 252 need not be the same as the additional conductive materialoverlaying “fingers” 254.

The sectional views of FIGS. 55 and 56 embody the use of article 250 or260 to achieve a series connected structural array of photovoltaic cells10. In FIG. 55, an article designated as 270 has been formed bycombining article 260 with cell 10 by laminating the bottom surface 240of article 260 to the top conductive surface 59 of cell 10. In apreferred embodiment, exposed surface 240 (those regions not coveredwith “fingers” 254) is formed by a material having adhesive affinity tosurface 59 and a secure and extensive adhesive bond forms betweensurfaces 240 and 59 during the heat and pressure exposure of thelamination process. Thus an adhesive “blanket” holds conductive material266 of “fingers” 254 in secure ohmic contact with surface 59. Aspreviously pointed out, low melting point alloys or conductive adhesivesmay also be considered to enhance this contact. It is understood thatarticle 270 of FIG. 55 is yet another embodiment of a “tabbed cellstock”.

The sectional view of FIG. 56 embodies multiple articles 270 arranged ina series interconnected array. The series connected array is designatedby numeral 290 in FIG. 56. In the FIG. 56 embodiment, it is seen that“fingers” 252 positioned on surface 238 of article 270 b have beenbrought into contact with the bottom surface 66 of cell 10 associatedwith article 270 a. This contact is achieved by choosing material 232forming free surface 238 of article 270 b to have adhesive affinity forbottom conductive surface 66 of cell 10 of article 270 a. Secureadhesive bonding is achieved during the heat and pressure exposure of alaminating process thereby resulting in a hold down of the “fingers”252. The ohmic contact thus achieved can be enhanced using low meltingpoint alloys or conductive adhesives as previously taught herein.

Thus, it is seen in the FIG. 56 embodiment that continuous communicationis achieved between the top surface of one cell and the bottom or rearsurface of an adjacent cell. Importantly, the communication is achievedwith a continuous, monolithic conductive structure. This avoids addedresistances and potential degradation of contacts sometimes associatedwith multiple contact surfaces when using other techniques, such asconductive adhesives and solders, to conductively join a multiplecomponent conductive path. In addition, the FIG. 56 embodiment clearlyshows an advantageous “shingling” type structure that avoids anyshielding of valuable photovoltaic cell surface. Conversely, the FIG. 56structure avoids any substantial separation between adjacent cells.Finally, it is seen that the structural embodiment of FIG. 56 includescomplete encapsulation of cells 10.

The embodiments of FIGS. 50 through 52 show the “fingers” and “busses”as essentially planar rectangular structures. Other geometrical formsare clearly possible. This is especially the case when consideringstructure for contacting the rear or bottom surface 66 of a photovoltaiccell 10. One embodiment of an alternate structure is depicted in FIGS.53 and 54. FIG. 53 is a top plan view while FIG. 54 is a sectional viewtaken substantially from the perspective of lines 54-54 of FIG. 53. InFIGS. 53 and 54, there is depicted an article 275 analogous to article250 of FIG. 50. The article 275 in FIGS. 53 and 54 comprises “fingers”280 similar to “fingers” 254 of the FIG. 50 embodiment. However, thepattern of material 251 forming the structure on the top surface 238 aof article 275 is considerably different than the “fingers” 252 and“buss” 256 of the FIG. 50 embodiment. In FIG. 53, material 251 a isdeposited in a mesh-like pattern having voids 276 leaving multipleregions of surface 238 a exposed. Lamination of such a structure mayresult in improved surface area contact of the pattern compared to thefinger structure of FIG. 50. It is emphasized that since surface 238 aof article 275 eventually contacts rear surface 66 of the photovoltaiccell, potential shading is not an issue and thus geometrical design ofthe exposed contacting surfaces 238 a relative to the mating conductivesurfaces 66 can be optimized without consideration to shading issues.

In the present specification lamination has been shown as a means ofcombining the collector grid or electrode structures with a conductivesurface. However, one will recognize that other application methods tocombine the grid or electrode with a conductive surface may beappropriate such as transfer application processing. For example, in theembodiments such as those of FIG. 23 or 33, the substrate is shown toremain in its entirety as a component of the “tabbed cell stock” andfinal interconnected array. However, this is not a requirement. In otherembodiments, all or a portion of the substrate may be removed prior toor after a laminating process accomplishing positioning and attachmentof “fingers” 84 and “busses” 86 to a conductive cell surface. In thiscase, a suitable release material (not shown) may be used to facilitateseparation of the conductive collector electrode structure from aremoved portion of substrate 70 during or following an application suchas the lamination process depicted in FIG. 21. Thus, in this case theremoved portion of substrate 70 would serve as a surrogate or temporarysupport to initially manufacture and transfer the grid or electrodestructure to the desired conductive surface. One example would be thatsituation where layer 72 of FIG. 7 would remain with the finalinterconnected array while layers 74 and/or 76 would be removed.

Using a laminating approach to secure the conductive grid materials to aconductive surface involves some design and performance “tradeoffs”. Forexample, if the electrical trace or path “finger” 84 comprises a wireform, it has the advantage of potentially reducing light shading of thesurface (at equivalent current carrying capacity) in comparison to asubstantially flat electrodeposited, printed, etched or die cut foilmember. However, the relatively higher profile for the wire form must beaddressed. It has been taught in the art that wire diameters as small as50 micrometers (0.002 inch) can be assembled into grid like arrangementsonto photovoltaic cell surfaces prior to applying sealing materials.Thus when laid on a flat surface such a wire would project above thesurface 50 micrometers (0.002 inches). For purposes of this instantspecification and claims, a structure projecting above a surface lessthan 50 micrometers (0.002 inches), i.e. 1 micrometer, 5 micrometer, 10micrometer 25 micrometer, 50 micrometer, will be defined as a lowprofile structure. Often a low profile structure may be furthercharacterized as having a substantially flat surface.

A potential cross sectional view of a wire form 84 d after beinglaminated to a surface is depicted in FIG. 57. FIG. 58 depicts a typicalcross sectional view of an electrical trace 84 e formed by printing,electrodeposition, chemical “electroless” plating, foil etching orstamping, masked vacuum deposition etc. It is seen in FIG. 57 that beinground the wire itself contacts the surface essentially along a line(normal to the paper in FIG. 57). In addition, the wire form is embeddedin the sealing material, but the sealing material forming surface 80 dof film 70 may have difficulty flowing completely around the wire,leaving voids as shown in FIG. 57 at 99, possibly leading to insecurecontact. Thus, the thickness of the sealing layer and laminationparameters and material choice become very important when using a roundwire form. On the other hand, using a lower profile substantially flatconductive trace such as depicted in FIG. 58 increases contact surfacearea compared to the line contact associated with a wire. The lowprofile form of FIG. 58 is easily embedded into the sealing layerpromoting broad surface contact and secure lamination but comes at theexpense of increased light shading for equivalent current carryingcapacity. The low profile, flat structure does require consideration ofthe thickness of the “flowable” sealing layer forming surface 80 erelative to the thickness of the conductive trace. Excessive thicknessof certain sealing layer materials might allow relaxation of the“blanket” pressure promoting contact of the surfaces 98 with a matingconductive surface such as 59. Insufficient thickness may lead to voidssimilar to those depicted for the wire forms of FIG. 57. However,testing has indicated that sealing layer thicknesses for low profiletraces such as embodied in FIG. 58 ranging from 0.5 mil (0.0005 inch) to10 mil (0.01 inch) all perform satisfactorily. Thus a wide range ofthickness is possible, and the invention is not limited to sealing layerthicknesses within the stated tested range.

A low profile structure such as depicted in FIG. 58 may be advantageousbecause it may allow minimizing sealing layer thickness and consequentlyreducing the total amount of functional groups present in the sealinglayer. Such functional groups may adversely affect solar cellperformance or integrity. For example, it may be advantageous to limitthe thickness of a sealing layer such as EVA to 3 mils or less whenusing a CIS or CIGS photovoltaic material.

Electrical contact between conductive grid “fingers” or “traces” 84 anda conductive surface (such as cell surface 59) may be further enhancedby coating a conductive adhesive formulation onto “fingers” 84 andpossibly “busses” 86 prior to or during the lamination process such astaught in the embodiment of FIG. 21. In a preferred embodiment, theconductive adhesive would be a “hot melt” material. A “hot melt”conductive adhesive would melt and flow at the temperatures involved inthe laminating process 92 of FIG. 21. In this way surface 98 (see FIGS.14 and 15) is formed by a conductive adhesive resulting in secureadhesive and electrical joining of grid “fingers” 84 to a conductivesurface such as top surface 59 following the lamination process. Inaddition, such a “flowable” conductive material may assist in reducingvoids such as depicted in FIG. 57 for a wire form. In addition, a“flowable” conductive adhesive may increase the contact area for a wireform 84 d.

In the case of a low profile form such as depicted in FIG. 58, theconductive adhesive may be applied by standard registered printingtechniques. However, it is noted that a conductive adhesive coating fora low profile conductive trace may be very thin, of the order of 0.1 to10 micrometer thick. Thus, the intrinsic resistivity of the conductiveadhesive can be relatively high, perhaps up to or even exceeding about100 ohm-cm. This fact allows reduced loading and increased choices for aconductive filler. Since the conductive adhesive does not require heavyfiller loading (i.e. it may have a relatively high intrinsic resistivityas noted above) other unique application options exist.

For example, a suitable conductive “hot melt” adhesive may be depositedfrom solution onto the surface of the “fingers” and “busses” byconventional paint electrodeposition techniques. Alternatively, should acondition be present wherein the exposed surface of fingers and bussesbe pristine (no oxide or tarnished surface), the well knowncharacteristic of such a surface to “wet” with water based formulationsmay be employed to advantage. A freshly activated or freshlyelectroplated metal surface will be readily “wetted” by dipping in awater-based polymer containing fluid such as a latex emulsion containinga conductive filler such as carbon black. Application selectivity wouldbe achieved because the exposed polymeric sealing surface 80 would notwet with the water based latex emulsion. The water based material wouldsimply run off or could be blown off the sealing material using aconventional air knife. However, the water based film forming emulsionwould cling to the freshly activated or electroplated metal surface.This approach is similar to applying an anti-tarnish or conversion dipcoating to freshly electroplated metals such as copper and zinc.

Alternatively, one may employ a low melting point metal-based materialas a constituent of the material forming either or both surfaces 98 and100 of “fingers” and “busses”. In this case the low melting pointmetal-based material, or alloy, melts during the temperature exposure ofthe process 92 of FIG. 21 (typically less than 325 degrees Centigrade)thereby increasing the contact area between the mating surfaces 98, 100and a conductive surface such as 59. Alternatively, induction heatingmay be suitable to sufficiently heat the conductive metallic pattern.Such low melting point metal-based materials may be applied byelectrodeposition or simple dipping to wet the underlying conductivetrace. Suitable low melting point metals may be based on tin, such astin-bismuth and tin-lead alloys. Such alloys are commonly referred to as“solders”. In another preferred embodiment indium or indium containingalloys are chosen as the low melting point contact material at surfaces98, 100. Indium melts at a low temperature, considerably below possiblelamination temperatures. In addition, indium is known to bond to glassand ceramic materials when melted in contact with them. Given sufficientlamination pressures, only a very thin layer of indium or indium alloywould be required to take advantage of this bonding ability.

In yet another embodiment, one or more of the layers 84, 86, 88, 90 etc.may comprise a material having magnetic characteristics. Magneticmaterials include nickel and iron. In this embodiment, either a magneticmaterial in the cell substrate or the material present in thefinger/grid collector structure is caused to be permanently magnetized.The magnetic attraction between the “grid pattern” and magneticcomponent of the foil substrate of the photovoltaic cell (or visa versa)creates a permanent “pressure” contact.

In yet another embodiment, the “fingers” 84 and/or “busses” 86 comprisea magnetic component such as iron or nickel and a external magneticfield is used to maintain positioning of the fingers or busses duringthe lamination process depicted in FIG. 21.

A number of methods are available to employ the current collecting andinterconnection structures taught hereinabove with photovoltaic cellstock to achieve effective interconnection of multiple cells intoarrays. A brief description of some possible methods follows. A firstmethod envisions combining photovoltaic cell structure with currentcollecting electrodes while both components are in their originallyprepared “bulk” form prior to subdivision to dimensions appropriate forindividual cells. An expansive surface area of photovoltaic structuresuch as embodied in FIGS. 1 and 2 of the instant specificationrepresenting the cumulative area of multiple unit cells is produced. Asa separate and distinct operation, an array comprising multiple currentcollector electrodes arranged on a common substrate, such as the arrayof electrodes taught in FIGS. 9 through 15 is produced. The bulk arrayof electrodes is then combined with the expansive surface ofphotovoltaic structure in a process such as the laminating processembodied in FIG. 21. This process results in a bulk combination ofphotovoltaic structure and collector electrode. Appropriate subdividingof the bulk combination results in individual cells having apre-attached current collector structure. Electrical access to thecollector structure of individual cells may be achieved using throughholes, as taught in conjunction with the embodiments of FIGS. 35 through42. Alternatively, one may simply lift the collector structure away fromthe cell surface 59 at the edge of the unit photovoltaic cell to exposethe collector electrode.

Another method of combining the collector electrodes and interconnectstructures taught herein with photovoltaic cells involves a first stepof manufacture of multiple individual current collecting structures orelectrodes. A suitable method of manufacture is to produce a bulkcontinuous roll of electrodes using roll to roll processing. Examples ofsuch manufacture are the processes and structures embodied in thediscussion of FIGS. 9 through 15 of the instant specification. The bulkroll is then subdivided into individual current collector electrodes forcombination with discrete units of cell stock. The combination producesdiscrete individual units of “tabbed” cell stock. In concept, thisapproach is appropriate for individual cells having known and definedsurface dimensions, such as 6″×6″, 4″×3″, 2″×8″ and 2″×16″. Cells ofsuch defined dimensions may be produced directly, such as withconventional crystal silicon manufacture. Alternatively, cells of suchdimension are produced by subdividing an expansive cell structure intosmaller dimensions. The “tabbed” cell stock thereby produced could bepackaged in cassette packaging. The discrete “tabbed” cells are thenelectrically interconnected into an array, optionally using automaticdispensing, positioning and electrical joining of multiple cells. Theoverhanging tabs of the individual “tabbed” cells facilitate suchjoining into an array as was taught in the embodiments of FIGS. 24, 34,43, and 56 above.

Alternate methods to achieve interconnected arrays according to theinstant invention comprise first manufacturing multiple currentcollector structures in bulk roll to roll fashion. In this case the“current collector stock” would comprise electrically conductive currentcollecting structure on a supporting sheetlike web essentiallycontinuous in the “Y” or “machine” direction. Furthermore, theconductive structure is possibly repetitive in the “X” direction, suchas the arrangement depicted in FIGS. 9, 12 and 38 of the instantspecification. In a separate operation, individual rolls of unit “cellstock” are produced, possibly by subdividing an expansive web of cellstructure. The individual rolls of unit “cell stock” are envisioned tobe continuous in the “Y” direction and having a defined widthcorresponding to the defined width of cells to be eventually arranged ininterconnected array.

Having separately prepared rolls of “current collector stock” and unit“cell stock”, multiple assembly processes may be considered to assemblemodules as follows. In one form of array assembly process, a roll ofunit “current collector stock” is produced, possibly by subdividing abulk roll of “current collector stock” to appropriate width for the unitroll. The rolls of unit “current collector stock” and unit “cell stock”are then combined in a continuous process to produce a roll of unit“tabbed stock”. The “tabbed” stock therefore comprises cells, which maybe extensive in the “Y” dimension, equipped with readily accessiblecontacting surfaces for either or both the top and bottom surfaces ofthe cell. The “tabbed” stock may be assembled into an interconnectedarray using a multiple of different processes. As examples, two suchprocess paths are discussed according to (A) and (B) following.

Process Example (A)

Multiple strips of “tabbed” stock are fed to a process such that aninterconnected array of multiple cells is achieved continuously in themachine (original “Y”) direction. This process would produce aninterconnected array having series connections of cells whose numberwould correspond to the number of rolls of “tabbed” stock being fed. Inthis case the individual strips of “tabbed” stock would be arranged inappropriate overlapping fashion as dictated by the particular embodimentof “tabbed” stock. The multiple overlapping tabbed cells would beelectrically joined appropriately using electrical joining means,surface mating through laminating or combinations thereof as has beentaught above. Both the feed and exit of such an assembly process wouldbe substantially in the original “Y” direction and the output of such aprocess would be essentially continuous in the original “Y” direction.The multiple interconnected cells could be rewound onto a roll forfurther processing.

Process Example (B)

An alternative process is taught in conjunction with FIGS. 59 and 60.FIG. 59 is a top view of the process and FIG. 60 is a perspective view.The process is embodied in FIGS. 59 and 60 using the “tabbed cell stock”270 as shown in FIG. 55. One will recognize that other forms of “tabbedcell stock” such as those shown in FIGS. 23, 33, 42, are also suitable.A single strip of “tabbed” cell stock 270 is unwound from roll 300 andcut to a predetermined length “Y-59”. “Y-59” represents the width of theform factor of the eventual interconnected array. The strip of “tabbedcell stock” cut to length “Y-59” is then positioned. In the embodimentof FIGS. 59 and 60 the strip is securely positioned on vacuum belt 302.The strip is then “shuttled” in the original “x” direction of the“tabbed cell stock” a distance substantially the length of a repeatdimension among adjacent series connected cells. This repeat distance isindicated in FIGS. 56 and 59 as “X-10”. A second strip of “tabbed cellstock” 270 is then unwound and appropriately positioned to properlyoverlap the first strip, as best shown in FIG. 56. This second strip iscut to length “Y-59”. The second strip is then slightly tacked to thefirst strip of “tabbed cell stock” using exposed substrate material, asthat indicated at numeral 306 in FIG. 56. The tacking may beaccomplished quickly and simply at points spaced in the “Y-59” directionusing heated probes to melt small regions of the sealing materialforming the surface of the exposed substrate. This process ofpositioning and tacking is repeated multiple times. It is understoodthat methods other than tacking may be chosen to maintain positioning ofthe adjacent cells prior to lamination. Eventually, the repetitivestructures are passed through a lamination step. In the embodiment ofFIGS. 59 and 60, the lamination is accomplished using roll laminator310. Thus the series connected structure 290 depicted in FIG. 56 isachieved. The electrical joining may take many forms, depending somewhaton the structure of the individual “tabbed cell stock”. For example, inthe embodiment of FIGS. 24 and 25, joining may take the form of anelectrically conductive adhesive, solder, etc. as previously taught. Inthe case of “tabbed” cell stock such as FIG. 55, electrical joining maycomprise a simple adhesive “blanket hold down” lamination such asembodied in FIG. 56, but may also include additional conductiveadhesives. It is seen that in the process depicted in FIGS. 59 and 60the interconnected cell stock would exit the basic lamination assemblyprocess in a fashion substantially perpendicular to the original “Y”direction of the “tabbed cell stock”. The interconnected cells producedwould therefore have a new predetermined width “Y-59” and the new length(in the original “X” direction) may be of extended dimension. The outputin the new length dimension may be described as essentially continuousand thus the output of interconnected cells may be gathered on roll 320as shown.

While the feed material in the process embodiment of FIGS. 59 and 60 isshown as a continuous strip of “tabbed cell stock” 270, one willunderstand that the process may alternatively be practiced using definedlengths (Y-59) of “tabbed cell stock” fed from, for example, a cassetteof lengths sorted according to performance characteristics.

It will be appreciated that using the processing as embodied in FIGS. 59and 60, a large choice of final form factors for the interconnectedarray is possible. For example, dimension “Y-59” could conceivably andreasonably be quite large, for example 8 feet while dimension “X-59” maybe virtually any desired dimension. To date, module sizes have beenrestricted by the practical problems of handling and interconnectinglarge numbers of small individual cells. The largest commerciallyavailable module known to the instant inventor is about 60 square feet.Using the instant invention, module sizes far in excess of 60 squarefeet are reasonable. Large modules suitable for combination withstandard construction materials may be produced. For example, a modulesurface area of 4 ft. by 8 ft. (a standard dimension for plywood andother sheetlike construction materials) is readily produced using theprocessing of the instant invention. Alternatively, since the finalmodular array can be accumulated in roll form as shown in FIGS. 59 and60, installation could be facilitated by the ability to simply “rollout” the array at the installation site. The ability to easily makemodular arrays of very expansive surface and having wide choice of formfactor greatly facilitates eventual installation and is a substantialimprovement over existing options for modular array manufacture.

It is further pointed out that additional optional operations may beachieved after or during the formation of modular arrays such as thoseof FIGS. 24, 34, 43, and 56 are formed. For example, additional filmstructure such as barrier layers can be added just prior to thelamination step depicted at rolls 310 in FIG. 60 or in an additionallamination step. Alternatively, the continuous output 290 of the FIG. 59process may be fed to additional process steps. For example, the modularstructure 290 of FIG. 59 may be cut to predetermined lengths in the“X-59” dimension for positioning into a casing of predetermineddimensions and/or further protected with a layer such as glass. Thiswould of course eliminate the delicate and careful handling associatedwith placements multiple cells interconnected with conventional “stringand tab” structure.

Finally, the modularization processes described by way of example abovein paragraphs 245 through 249 are very scaleable since they adoptlaminating processing firmly established in the packaging industry.

Example 1

A standard plastic laminating sheet from GBC Corp. 75 micrometer (0.003inch) thick was coated with DER in a pattern of repetitive fingersjoined along one end with a busslike structure resulting in an articleas embodied in FIGS. 16 through 19. The fingers were 0.020 inch wide,1.625 inch long and were repetitively separated by 0.150 inch. Thebuss-like structure which contacted the fingers extended in a directionperpendicular to the fingers as shown in FIG. 16. The buss-likestructure had a width of 0.25 inch. Both the finger pattern andbuss-like structure were printed simultaneously using the same DER inkand using silk screen printing. The DER printing pattern was applied tothe laminating sheet surface formed by the sealing layer (i.e. thatsurface facing to the inside of the standard sealing pouch).

The finger/buss pattern thus produced on the lamination sheet was thenelectroplated with nickel in a standard Watts nickel bath at a currentdensity of 50 amps. per sq. ft. Approximately 4 micrometers of nickelthickness was deposited to the overall pattern.

A photovoltaic cell having surface dimensions of 1.75 inch wide by2.0625 inch long was used. This cell was a CIGS semiconductor typedeposited on a 0.001 inch stainless steel substrate. A section of thelaminating sheet containing the electroplated buss/finger pattern wasthen applied to the top, light incident side of the cell, with theelectroplated grid finger extending in the width direction (1.75 inchdimension) of the cell. Care was taken to ensure that the buss region ofthe conductive electroplated metal did not overlap the cell surface.This resulted in a total cell surface of 3.61 sq. inch. (2.0625″×1.75″)with about 12% shading from the grid, (i.e. about 88% open area for thecell).

The electroplated “finger/buss” on the lamination film was applied tothe photovoltaic cell using a standard Xerox office laminator. Theresulting completed cell showed good appearance and connection.

The cell prepared as above was tested in direct sunlight forphotovoltaic response. Testing was done at noon, Morgan Hill, Calif. onApr. 8, 2006 in full sunlight. The cell recorded an open circuit voltageof 0.52 Volts. Also recorded was a “short circuit” current of 0.65 Amps.This indicates excellent power collection from the cell at highefficiency of collection.

Example 2

Individual thin film CIGS semiconductor cells comprising a stainlesssteel supporting substrate 0.001 inch thick were cut to dimensions of7.5 inch length and 1.75 inch width.

In a separate operation, multiple laminating collector grids wereprepared as follows. A 0.002 inch thick film of Surlyn material wasapplied to both sides of a 0.003 inch thick PET film to produce astarting laminating substrate as embodied in FIG. 44. Holes having a0.125 inch diameter were punched through the laminate to produce astructure as in FIG. 48. A DER ink was then printed on opposite surfacesand through the holes to form a pattern of DER traces. The resultingstructure resembled that depicted in FIG. 51. The grid fingers 254depicted in FIGS. 50 and 51 were 0.012 inch wide and 1.625 inch long andwere spaced on centers 0.120 inch apart in the length direction. Thegrid fingers 252 were 0.062 inch wide and extended 1 inch and werespaced on centers 0.5 inch apart. The printed film was thenelectroplated to deposit approximately 2 micrometers nickel strike, 5micrometers copper and a top flash coating of 1 micrometer nickel. Thisoperation produced multiple sheets of laminating current collector stockhaving overall dimension of 7.5 inch length (“Y” dimension) and 4.25 inwidth (“X” dimension) as indicated in FIG. 50. These individual currentcollector sheets were laminated to cells having dimension of 7.25 inchesin length and 1.75 inches in width to produce tabbed cell stock asdepicted in FIG. 55. A standard Xerox office roll laminator was used toproduce the tabbed cell stock. Six pieces of the tabbed cell stock werelaminated together as depicted in FIG. 56. A standard Xerox office rolllaminator was used to produce the FIG. 56 embodiment. The combinedseries interconnected array had a total surface area of 76.1 squareinches. In full noon sunlight the 6 cell array had an open circuitvoltage of 3.2 Volts and a short circuit current of 2.3 amperes.

While many of the embodiments of the invention refer to “currentcollector” structure, one will appreciate that similar articles could beemployed to collect and convey other electrical characteristics such asvoltage.

One application of the modules made practical by the teachings above isexpansive area photovoltaic energy farms or expansive area rooftopapplications. The instant invention envisions facile manufacture andinstallation of large sheetlike modules having area dimensions suitablefor covering expansive surface areas. Practical module widths may be 2ft., 4 ft., 8 ft etc. Practical module lengths may be 2 ft., 4 ft., 10ft., 50 ft, 100 ft., 500 ft., or larger. The “sheetlike” modules may beproduced in a wide range of forms. The longer lengths can becharacterized as “continuous” and be shipped and installed in a rollformat. In another application, the sheetlike modules may be adhered toa rigid supporting member such as plywood, polymeric sheet or ahoneycomb structure. The sheetlike modules may be produced havingterminal bars at two opposite terminal ends of the module. Theseterminal bars are easily incorporated into the modules using the samecontinuous processes used in assembly of the bulk module. It is notedthat in the hereinbefore teachings, the terminal bars may haveoppositely facing conductive surface regions with electricalcommunication between them. This is an advantage for certain embodimentsof the instant invention, in that an upward facing conductive surfacefor the terminal bars may facilitate electrical connections.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications,alternatives and equivalents may be included without departing from thespirit and scope of the inventions, as those skilled in the art willreadily understand. Such modifications, alternatives and equivalents areconsidered to be within the purview and scope of the invention andappended claims.

1. An article comprising a combination of a first photovoltaic cell andan interconnection component, said first photovoltaic cell comprisingsemiconductor material and having a light incident, upward facing topsurface formed of a transparent or translucent first conductivematerial, said interconnection component being flexible and furthercomprising a substrate having a sheetlike form whereby said substratehas length and width, wherein the length and width are greater thanthickness, said substrate comprising one or more polymeric layers, andfurther having a downward facing first side and an upward facing secondside, said interconnection component further characterized as having acollection region and an interconnection structure, said collectionregion comprising a transparent or translucent portion of said substratewherein the downward facing first side is formed of the one or morepolymeric layers, said collection region further characterized as havinga pattern comprising a second electrically conductive material, saidpattern positioned directly on said first side, and not including any ofsaid first conductive material forming said top surface of said firstphotovoltaic cell, said interconnection structure comprising additionalelectrically conductive material extending from said first side to saidsecond side of said substrate, and further extending over a portion ofsaid second side, said additional conductive material being in ohmicelectrical communication with said second electrically conductivematerial of said pattern, said combination characterized as having saidportion of said substrate associated with said collection regionoverlaying said light incident top surface of said first photovoltaiccell such that a portion of said second electrically conductive materialof said pattern is in direct physical contact with said transparent ortranslucent first conductive material forming said light incident topsurface of said first photovoltaic cell and, said pattern extends over apreponderance of said light incident surface.
 2. The article of claim 1wherein portions of said second electrically conductive material andsaid additional electrically conductive material comprise a monolithicmaterial common to both portions.
 3. The article of claim 2 wherein saidcommon monolithic material comprises a continuous metal.
 4. The articleof claim 1 wherein at least a portion of said first side of saidsubstrate associated with said collection region is formed by a materialhaving adhesive affinity for said light incident top surface.
 5. Thearticle of claim 1 wherein said article has a length much greater thanwidth whereby said article can be characterized as continuous in length.6. The article of claim 1 wherein said article is flexible.
 7. Thearticle of claim 1 wherein said pattern comprises multiple substantiallyparallel line segments.
 8. The article of claim 7 wherein two or more ofsaid parallel line segments comprise a common monolithic material. 9.The article of claim 1 wherein portions of said pattern are defined byprinted material.
 10. The article of claim 9 wherein said printedmaterial is characterized as having the ability to facilitate metaldeposition.
 11. The article of claim 1 wherein said pattern comprisesnickel.
 12. The article of claim 1 wherein said portion of said patternin contact with said light incident surface comprises a metalliccoating, said coating being absent polymeric material.
 13. The articleof claim 12 wherein said metallic coating comprises nickel.
 14. Thearticle of claim 1 wherein said pattern comprises an electricallyconductive polymer.
 15. The article of claim 14 wherein saidelectrically conductive polymer has adhesive affinity to said lightincident surface.
 16. The article of claim 1 wherein said photovoltaiccell comprises a self supporting metal based foil and wherein saidsemiconductor material covers the full expanse of an upward facingsurface of said metal based foil.
 17. The article of claim 1 furthercomprising, a second photovoltaic cell, said second cell having anelectrically conductive bottom surface portion facing away from a lightincident top surface and formed by a metal-based foil, and said secondcell being positioned such that said conductive bottom surface portionof said second cell overlays at least a portion of said interconnectionstructure, and wherein said pattern portion in direct physical contactwith said transparent or translucent first conductive material formingthe light incident top surface of said first photovoltaic cell and atleast a portion of said additional electrically conductive materialextending from said first side to said second side of said substratecomprise a monolithic material common to both portions, and wherein saidmonolithic material is in direct physical contact with said electricallyconductive bottom surface of said second cell.
 18. The article of claim17 wherein both said first and second cells have terminal edges definedby the extent of said semiconductor material, said first and secondcells being interconnected in series, and wherein said article iscapable of achieving series connection without requiring eitheroverlapping of said cells or substantial separation of adjacent terminaledges of said cells in a direction parallel to said light incidentsurfaces.
 19. The article of claim 1 wherein said transparent ortranslucent conductive material comprises a transparent conductiveoxide.
 20. The article of claim 1 wherein said electrical communicationbetween said additional conductive material extending over said secondside and said pattern is established using holes extending through saidsubstrate from said first side to said second side, wherein a portion ofsaid additional electrically conductive material extends through saidholes to electrically connect said second electrically conductivematerial of said pattern positioned on said first side of said substrateand said additional electrically conductive material extending over saidsecond side of said substrate.
 21. The article of claim 1 wherein saidpattern comprises a directly electroplateable resin (DER).
 22. Thearticle of claim 1 wherein either of said pattern or said additionalelectrically conductive material comprises metal with a melting point ator below the melting point of tin.
 23. The article of claim 4 whereinsaid material having adhesive affinity is a thermoplastic, whereby saidmaterial becomes fluid when temperatures and pressure are increasedsufficiently above ambient.
 24. The article of claim 4 wherein saidmaterial having an adhesive affinity for said light incident top surfaceis a polymeric adhesive and overlays a preponderance of said lightincident cell surface.
 25. The article of claim 1 wherein said portionof said first side of said substrate associated with said collectionregion and said light incident cell surface face each other and aremaintained in direct physical contact through adhesive bonding.
 26. Thearticle of claim 7 wherein an adjacent pair of said line segments aresubstantially parallel to each other over a length greater than onecentimeter and wherein there is no second electrically conductivematerial associated with said pattern extending between said linesegments throughout said length greater than one centimeter.
 27. Thearticle of claim 1 wherein said pattern comprises a monolithic materialextending throughout the entirety of said pattern.
 28. The article ofclaim 1 wherein said photovoltaic cell is flexible.
 29. The article ofclaim 7 wherein a connecting conductive material extends between anendpoint of a first of said parallel line segments to an endpoint of asecond of said parallel line segments and wherein said connectingconductive material and portions of said parallel line segments comprisea common continuous monolithic metal form.